The standard sized metal Lip Adapter that comes with all the 4 Point Wheel Alignment Clamps.  This is a SINGLE Lip Adapter.  Each 4 point clamp requires a total of 4 of these.

The Metal Lip Adapter is suitable for steel wheels, but extra care should be taken when using these metal components on an alloy or powder coated wheel as damage may result.  It is highly recommended that metal components not be used on alloy or powder coated wheels.

The metal lip adapters are designed to allow the clamp to grab the outer edge of a steel wheel tightly thus holding the entire clamp assembly to the tire and wheel.

The metal lip adapter is NOT normally used with any clamps that have grabber arm assemblies.  Clamps with grabber arm assemblies use plastic versions of the lip adapter as a means of locating the clamp and are not designed to actually hold the clamp onto the wheel.  That's what the grabber assembly does on those types of clamps.