These L-1, L-3, and 6-step tapered pipe threaded plug gauges are used to perform tolerance checks when inspecting internal tapered pipe threads. They are available as individual gauge members or as part of an assembly with a taperlock handle. L-1 plug gauges test if the threads are at the high or low limit and establish the reference when hand-tightened. L-3 inspection is performed by wrench-tightening based on the L-1 inspection. 6-Step plugs are used for a thread crest inspection when specifications require it.