The Snap-on Steel Chrome Adaptors, No. EEPV6G3PK, provide direct engagement in deep spark plug wells, which help to save time on engine service and repair, according to the company. The Steel Chrome Adaptors offer a solution for spark plug wells when testing piston ring, valve, head gasket and other engine compression issues. The solid shank design works for deep, recessed wells and its knurled end allows for hand tightening helping prevent overtorqueing and cross threading. The 3-pc, chrome‐plated adapters connect to existing Snap‐on Compression Gauge (No. EEPV500) or gauge (No. EEPV6‐300G) and coupler. The adapters fit three spark plug hole sizes: M12L, M14S or M14L.