This teflon ring is the top insulator in the lower section nozzle body of the Non Contact Cutting Head on a Mark II or NTX. This ring is replaced more often than the other 3 rings because of it's shape and location. It is located between the Copper Nut (M108U0) and the Copper Nozzle Holder (M105U0).
Mazak® Part # 46683301120