This cap protects the power supply end of a Hypertherm Powermax plasma torch cable. Specifically, I have tested this to fit on a PowerMax 65, though it should fit on 45, 85, 105, etc. also.

This is especially useful if you have both a hand torch and a CNC machine torch, so that you can protect the delicate air fittings of the torch that is not in use.

Why an $800 torch doesn't come with one of these from the factory is a mystery to me.