Choosing a cargo seal is not simply a matter of picking the strongest product. The right choice depends on cargo value, the container or equipment being secured, route risk, and the compliance rules that apply to the shipment.
A bolt seal vs cable seal vs plastic seal comparison cargo teams can use starts with the security requirement: bolt seals suit high-value container shipping and ISO 17712 requirements. Cable seals provide flexible tamper evidence for irregular latches, and plastic seals fit lower-risk, indicative applications.
ISO 17712 separates seals into Indicative, Security, and High Security classes, while CTPAT programs require H-class seals for applicable international cargo. That distinction matters before you compare convenience, fit, or procurement cost. For a broader selection framework, see the Security Seal Buying Guide for Every Cargo Type.
Start by understanding how each seal is built and what kind of barrier or evidence it provides. From there, you can match the seal to the cargo, equipment, and compliance exposure rather than treating all tamper-evident products as interchangeable.
What Are the Main Types of Cargo Security Seals?
The three main cargo security seal types are bolt seals, cable seals, and plastic seals. Each fits a different balance of physical strength, flexibility, tamper evidence, and compliance requirements.
ISO 17712 organizes seal strength into three classes: Indicative (I), Security (S), and High Security (H). The right choice depends on the cargo, equipment, route, and rules governing the shipment.
- Class I, Indicative: Designed to show whether access has occurred, but not to provide a substantial physical barrier.
- Class S, Security: Provides a stronger barrier and tamper evidence for applications with a higher security requirement.
- Class H, High Security: Intended for high-risk international cargo and tested for significant resistance to unauthorized entry.
Bolt seals for high-value container shipping
Bolt seals use a rigid, fixed design that is well suited to intermodal shipping containers. They are classified as high-security seals under ISO 17712 and are recommended for high-value container shipping. Removal generally requires a dedicated tool such as a bolt cutter, which creates a clear break in the seal rather than allowing casual removal. Our security seals for shipping containers guide covers this application in more detail.
Cable seals for flexible, irregular closures
Cable seals use a metal cable that can adapt to different latch configurations. That flexibility makes them useful for tanker trucks, rail cars, containers, and other equipment where a rigid bolt may not fit. They provide tamper evidence while accommodating varied closure points and operating conditions.
Plastic seals for indicative applications
Plastic seals are lightweight and practical when the primary need is a visible record of entry. They are commonly used for lightweight cargo, utility meters, warehouse bins, and similar applications. They are generally indicative rather than high-security, so they should not be treated as a substitute for a Class H seal on high-value international cargo.
Compliance requirements can determine the decision before cargo value does. Ocean Network Express requires containers arriving in the United States or Canada to use high-security seals that meet or exceed ISO 17712. For CTPAT-oriented or regulated shipping programs, confirm the required class, serialization, and documentation before loading.
Sources: U.S. Customs and Border Protection guidance on ISO 17712; Ocean Network Express container security seal standards.
Bolt Seals: Strength, Certification, and Best Applications
Bolt seals are built for high-security container shipping, where the seal must create a meaningful physical barrier and make unauthorized entry apparent. Their rigid design and high tensile strength resist casual removal, and a bolt cutter is typically required to cut one open. That makes them a stronger choice than an indicative plastic seal when cargo value, route risk, or international compliance requirements call for more than a visual tamper record.
What makes a bolt seal high security?
ISO 17712 separates seals into three classes: Indicative (I), Security (S), and High Security (H). A bolt seal should not be described as ISO 17712 H-class merely because it has a metal body or looks robust. The classification depends on documented testing and manufacturing controls.
For H-class certification, ISO 17712 testing evaluates the seal's barrier performance under several attack conditions, including:
- Tensile strength, or resistance to pulling forces
- Bending strength, or resistance to leverage
- Impact resistance against force such as hammering or crushing
- Shear strength, or resistance to cutting tools
The standard also requires independent third-party confirmation of physical strength and an audit of the manufacturer's security-related business processes. Before purchasing, request the manufacturer's current ISO 17712 test certificate, confirm the H mark, and verify that every seal carries a unique serial number. The U.S. Customs and Border Protection guidance explains the testing and audit requirements.
When are bolt seals the right choice?
For CTPAT participants, H-class seals are required for international cargo. Bolt seals are therefore a practical fit for export and import containers, especially when a shipping line, customs authority, or customer specification requires an ISO 17712 high-security seal. They are also well suited to high-value or theft-sensitive loads moving through multiple custody points, where a rigid, single-use seal provides a clear break indicator.
Bolt seals are not reusable. Once cut with a bolt cutter, they must be discarded and replaced. That single-use design supports controlled seal management: record the serial number at application, inspect it at each handoff, and document any mismatch or visible damage. For a closer look at how the options differ, read this bolt seals vs cable seals comparison. Choose a cable seal when an adjustable fit is more important than a rigid bolt. But use an H-class bolt seal when container compliance and maximum barrier strength are the priority.
Cable Seals: Flexibility, Reusability, and When They Are the Right Choice
Cable seals are built for cargo points that do not line up neatly. Their adjustable length lets operators secure irregularly shaped or mismatched latch assemblies, including configurations where a rigid bolt seal would not fit. That flexibility makes them a practical option for mixed fleets moving different equipment types across the same network.
The cable itself is typically galvanized or stainless steel, with common diameters ranging from 1.5 mm to 3.5 mm. The right diameter depends on the application and the level of cut resistance required. Thicker cable can provide greater resistance to cutting, while a smaller cable may be easier to route through tight or unusual latch points. Review the product specification and your security requirements together rather than treating every cable seal as interchangeable.
Where cable seals fit best
- Tanker trucks: Adjustable cable can pass through irregular manhole, valve, or latch assemblies where a fixed-length bolt seal is impractical.
- Rail cars: Cable seals can accommodate varied valve and closure configurations across a fleet.
- Mixed fleets and containers: One cable-seal format can give teams more application flexibility when trailers, containers, and specialized equipment use different locking points.
Cable seals provide tamper evidence and a higher barrier to entry than standard plastic pull-tight seals because the metal wire resists simple cutting tools. They are not automatically the right replacement for a high-security bolt seal, however. For international cargo subject to CTPAT or other customer requirements, confirm the seal's classification, documentation, and application procedure before standardizing it across shipments.
In a bolt seals vs cable seals comparison, the practical question is usually fit and workflow: choose a cable seal when adjustability matters, the fleet has varied latch designs, or operators need one adaptable format. Choose a bolt seal when a rigid, high-security barrier is required and the locking points support it.
Plastic Indicative Seals: Where They Are Appropriate and Where They Fall Short
Plastic indicative seals are a practical choice when the primary need is visible tamper evidence, not a physical barrier against forced entry. They are commonly used on lightweight cargo, utility meters, warehouse bins, and other low-value items where a broken or missing seal tells staff that an inspection is needed.
Where plastic seals make sense
For high-volume, low-value shipments, plastic seals can be a cost-effective way to support basic process control. Their lightweight construction and simple application make them useful when teams need to seal many access points quickly. A serialized or otherwise identifiable seal can also help connect a shipment, meter, bin, or compartment to an inspection record.
That value is operational rather than protective. Indicative seals are designed to show evidence of interference. They are not intended to withstand the same force or resist the same removal methods as a security or high-security seal. Treat them as an alert mechanism, not as the lock on the cargo.
Where plastic seals fall short
Plastic indicative seals are not high-security seals and are not ISO 17712-rated for high-security cargo. They should not be substituted for an approved bolt seal or another compliant product when the route, carrier, customer, or security program requires a Class H seal.
This distinction matters most for cross-border container movements. CTPAT programs require the use of H-class seals, and some carrier requirements specify high-security seals that meet or exceed ISO 17712. Using a non-compliant seal can expose the cargo owner to significant penalties under applicable shipping terms. Before loading, confirm the requirement for the route and destination rather than choosing a seal based only on unit cost.
In practical terms, use plastic indicative seals for low-risk, low-value applications where tamper visibility is enough. For international cargo, high-value loads, or shipments subject to formal security requirements, select a certified high-security seal and retain the supporting compliance documentation.
Bolt vs Cable vs Plastic: A Cargo Seal Comparison and Decision Matrix
The right seal depends on the physical closure, the value of the cargo, the route, and the compliance standard governing the shipment. Use this matrix to narrow the choice before requesting serialized products or documentation.
| Criterion | Bolt seals | Cable seals | Plastic seals |
|---|---|---|---|
| Security level | High-security barrier with rigid construction and high tensile strength. | Strong tamper-evident barrier when pulled tight; more adaptable than a rigid seal. | Indicative tamper evidence, not typically intended for high-security cargo protection. |
| ISO 17712 class | Commonly selected for High Security, or Class H, requirements when properly certified. | Classification depends on the specific certified product. Confirm the supplier's documentation. | Generally associated with Indicative, or Class I, applications rather than Class H. |
| Best cargo or equipment | High-value shipping containers and rigid locking bars or hasps. | Containers, tanker trucks, rail cars, and irregular or mismatched latch assemblies. | Lightweight cargo, warehouse bins, utility meters, and other low-value applications. |
| Recommended routes | International container routes and export shipments where high-security seals are required. | Routes using varied equipment or closures that require adjustable length and flexible placement. | Controlled domestic or facility routes where the main need is visible tamper indication. |
| Reusability | Plan for single-use application and replacement after removal. | Plan for single-use application and replacement after removal. | Plan for single-use application and replacement after removal. |
| Removal method | Requires a dedicated tool such as a bolt cutter. | Remove by cutting the cable with an appropriate tool. | Usually easier to remove than metal seals, depending on the design. |
| Cost profile | Quote-based and generally higher than indicative plastic options because of security and certification requirements. | Quote-based; pricing varies with cable construction, length, serialization, and volume. | Usually the lower-cost option for basic indicative applications; request a quote for volume pricing. |
Compliance should make the final decision, not cost alone. CTPAT programs require Class H seals for applicable international cargo, while carrier mandates may specify high-security seals meeting or exceeding ISO 17712. Confirm the route, carrier, and customer requirements before ordering. For a broader application review, see the Security Seal Buying Guide for Every Cargo Type.
Frequently Asked Questions
Which seal is best for an international shipping container?
For high-value container cargo, choose an ISO 17712 high-security bolt seal when the container hardware supports it. Its rigid construction creates a clear tamper-evident barrier, and it is designed for applications where compliance and physical resistance matter. Confirm the destination, carrier, and customer requirements before selecting the final seal.
When should I choose a cable seal instead of a bolt seal?
Choose a cable seal when the latch, valve, or closure has an irregular shape or requires an adjustable loop. Cable seals are useful on tanker trucks, rail cars, and containers because the cable can accommodate a wider range of attachment points. Select the cable diameter and construction according to the theft risk and required cut resistance.
Are plastic seals suitable for high-value cargo?
Usually, no. Plastic seals are primarily indicative seals for lightweight cargo, warehouse bins, utility meters, and other applications where the main need is to identify entry. They are not a substitute for a high-security seal when the shipment needs a physical barrier against intentional access.
How can I verify that a bolt seal meets ISO 17712 requirements?
Look for the appropriate high-security classification marking, request the manufacturer's test documentation, and confirm that each seal has a unique serial number. ISO 17712 requires independent confirmation of physical strength testing and an audit of the manufacturer's security-related business processes, according to U.S. Customs and Border Protection: ISO 17712 guidance.
Ready to Choose the Right Cargo Seal?
The right seal depends on your cargo, route, and compliance requirements. STiER can help you narrow the options and request a quote for a practical security seal solution. Request a quote for the right security seals for your cargo.