This is the Clutch Nut (Pilot Shaft) for the RC10GT. For Newer .12 OS Max engines. (See COMMENTS) Machined steel Has hex base for tightening One Clutch Nut One Clutch Nut Clip Works on all .12 size motors (except on O.S. CZ-Rs made before October, 1993. For these engines, use ASCC8804). This item is installed to keep the flywheel in place, and the clutch bell rides on this. It also has a groove that the e-clip fits into, and this retains the clutch bell. jlp 6/2/94 ir/jl &