SurLok®| RADSOK® Compression Lug

The RADSOK® SurLok® compression lug is a non-environmental, field-installable high-current lug that gives engineers a plug-and-play alternative to traditional bolt-on compression lugs. Built on Amphenol’s proven RADSOK® high-current contact technology, SurLok® delivers high ampacity, low contact resistance and repeatable mating performance for power distribution applications inside protected enclosures.

As the original SurLok® platform, this legacy non-environmental solution is ideal for indoor cabinets, racks and equipment where environmental sealing is not required but a robust, removable power interface is. For sealed, IP-rated, and more compact compression lugs designed for harsh environments and traction batteries, engineers should consider the newer SurLok Plus®  as the primary choice for new designs.

Table of Contents

• RADSOK SurLok Compression Lug Overview
• Key Features & Benefits
• How the SurLok System Works
• Typical Applications & Markets
• Installation, Tooling & Safety Considerations
• Choosing SurLok vs. SurLok Plus
• Specifications Overview
• Resources & Related RADSOK Solutions
• Engineer & Buyer FAQ

RADSOK® SurLok Compression Lug Overview

The SurLok® compression lug is a crimp-style power lug with a plastic snap-together housing designed to mate with a RADSOK® socket mounted on a busbar or laminated bus structure. Instead of permanently bolting down a traditional copper lug, SurLok® creates a removable, plug-in interface that helps simplify installation, maintenance and module replacement in power distribution equipment.

SurLok® is designed for use in protected environments where the connection point is located inside a cabinet, rack or enclosure. The lug is crimped to the cable with industry-standard compression tooling, then pushed onto the mating pin until the locking feature engages. A two-piece plastic housing snaps over the mated interface to provide touch protection and a clear visual indication of full engagement.

This non-environmental SurLok® platform supports high-current power distribution and is typically rated for high-voltage AC/DC systems when used within the limits defined in the latest Amphenol Industrial datasheets. For applications requiring environmental sealing, IP ratings, EMI options or HVIL, the SurLok Plus® family is recommended.

Key Features & Benefits

By combining compression lug concepts with RADSOK® high-current contact geometry, the SurLok® system delivers several advantages over traditional bolted lugs inside cabinets and racks:

• High ampacity in a compact interface – RADSOK® socket geometry increases contact surface area around the mating pin, supporting higher current capacity with reduced temperature rise compared to conventional contacts of similar size.
• Field-installable compression lug – Uses widely available U-indent, clamshell or 4-indenter crimp tools with standard color-coded dies for on-site cable termination.
• Plug-and-play power distribution – Creates a removable, high-current connection between cable and busbar, ideal for drawers, modules and subassemblies that require serviceability.
• Integral mechanical locking – The SurLok® lug locks onto the mating pin, and the two-piece plastic housing snaps into place, helping maintain mechanical retention while providing touch protection.
• Color-coded size identification – Industry-standard color coding aids in selecting the correct die and lug combination for the conductor size.
• Low contact resistance – High-conductivity copper alloy contacts with appropriate plating support efficient power transfer and minimized I²R losses.
• Proven materials and compliance – SurLok® components are designed to meet key connector and material compliance requirements as detailed in Amphenol product documentation.

How the SurLok System Works

At the core of each SurLok® interface is a RADSOK® socket contact. Unlike a solid cylindrical socket, RADSOK® uses a specialized grid structure to increase the effective contact surface area between the socket and mating pin. This allows high current to be carried at relatively low contact resistance while maintaining a manageable insertion force.

A typical RADSOK® SurLok® compression lug installation includes:

• Cable-side SurLok® lug – A compression lug containing the RADSOK® socket, crimped onto the conductor using standard compression tooling.
• Bus-side pin or stud – A threaded pin, stud or equivalent interface mounted to a busbar or laminated bus assembly inside the equipment.
• Two-piece plastic housing – A molded housing that snaps over the mated lug and pin to provide touch protection, strain relief and a visual indication that the connection is fully engaged.

Once the cable is terminated, the installer pushes the SurLok® lug straight onto the pin until the locking feature engages. When service is required, the lug can be removed without disturbing bolted joints or re-crimping the conductor, helping reduce downtime during maintenance or upgrades.

Typical Applications & Markets

The RADSOK® SurLok® compression lug is most often used in indoor or otherwise protected locations where high-current connections must be both reliable and serviceable. Typical applications include:

• Industrial power distribution cabinets – Switchgear, distribution boards and in-panel busbar systems within equipment rooms.
• UPS and backup power systems – Modular battery drawers, power shelves and hot-swappable power modules.
• Process control and factory automation – High-current DC bus connections inside control panels and equipment racks.
• Heavy equipment and rail interiors – Protected compartments where power modules are located away from direct environmental exposure.
• Test and measurement racks – High-current test stands and load banks that require quick connect/disconnect of power cables.
• Legacy energy storage and DC power shelves – Non-environmental cabinet installations where field-installable lugs are preferred.

For outdoor, mobile, or harsh-environment platforms where connectors are exposed to moisture, dust or road spray, the environmentally sealed SurLok Plus® heavy-duty power connector family is recommended instead of SurLok®.

Installation, Tooling & Safety Considerations

The RADSOK® SurLok® compression lug is designed to be installed using common compression tools already found in many electrical assembly and field service environments. The basic steps are:

• Cable preparation – Strip the conductor according to the guidelines in the SurLok® documentation, taking care not to nick or damage the strands.
• Crimp termination – Insert the stripped conductor into the SurLok® barrel and crimp using the correct U-indent, clamshell or 4-indenter die set matched to the wire size and color code.
• Mating and locking – Align the lug with the mating pin on the busbar and push until the locking feature engages.
• Housing installation – Snap the two-piece plastic housing over the mated lug and pin; verify that all latches are fully seated and that the assembly is secure.

SurLok® components are designed to work as part of complete equipment evaluated to applicable standards. For background on connector safety for power applications, international standardization bodies such as UL publish overviews of connector certification categories and requirements. Always follow local electrical codes, safety standards and the Amphenol product documentation when designing and installing SurLok® assemblies.

Choosing SurLok vs. SurLok Plus

SurLok® and SurLok Plus® share similar design goals—field-installable, high-current compression connections that leverage RADSOK® contact technology—but they target different types of applications.

• SurLok® 
  • Type: Non-environmental compression lug with snap-on plastic housing.
  • Best for: Indoor, cabinet-based power distribution where the interconnect is protected from direct environmental exposure.
  • Key benefits: Simple field installation with standard crimp tooling, removable plug-in connection to busbars, legacy compatibility with existing systems.
• SurLok Plus®
  • Type: Environmentally sealed heavy-duty power connector family with options for various keying, sizes, and advanced features.
  • Best for: EV/HEV traction batteries, energy storage systems, outdoor equipment and other harsh-environment power connections.
  • Key benefits: IP-rated sealing, compact envelopes, touch-proof design, and available configurations that support EMI management and HVIL in the system.

For new sealed, mobile or harsh-environment high-voltage platforms, Amphenol Industrial generally recommends designing in SurLok Plus® while continuing to support SurLok® as a proven non-environmental solution for protected cabinet installations.

Specifications Overview

The values below provide a general overview of typical SurLok® capabilities. Always consult the latest Amphenol Industrial datasheets for detailed, part-specific electrical, mechanical and environmental ratings.

Engineer & Buyer FAQ

• What is a RADSOK® SurLok® compression lug and where is it used?
  It is a non-environmental, field-installable high-current compression lug that mates with a RADSOK® socket on a busbar or laminated bus structure. It is used primarily in protected enclosures such as power distribution cabinets, UPS systems, control panels and equipment racks that require reliable, serviceable power connections.
• How is a SurLok® lug terminated and what crimp tools are required?
  SurLok® lugs are crimped to the conductor using industry-standard U-indent, clamshell or 4-indenter compression tools with the appropriate color-coded dies for the selected wire size. No proprietary crimp tooling is required.
• Is the SurLok® connection touch-safe?
  Once the lug is fully mated to the bus-side pin, the two-piece plastic housing snaps over the connection to provide touch protection and a clear indication that the assembly is properly engaged, when installed and serviced by trained personnel according to applicable standards.
• When should I choose SurLok® instead of SurLok Plus®?
  Choose SurLok® for non-environmental, protected installations inside cabinets or enclosures where IP-rated sealing is not required. Choose SurLok Plus® for new designs that involve outdoor, mobile or harsh-environment conditions, or where IP ratings, EMI options or HVIL functions are needed.
• Can SurLok® be used in new designs?
  Yes. SurLok remains suitable for new protected cabinet installations that benefit from a field-installable, plug-in bus connection. However, SurLok Plus® is generally preferred for most new harsh-environment, traction battery and outdoor energy storage platforms.
• Where can I find detailed ratings and part numbering for SurLok®?
  All detailed electrical, mechanical and environmental ratings, along with part numbering and assembly instructions, are provided in the latest SurLok® datasheets and product literature.