Push rod clutch adjuster in gearbox.
3/8 - 26 tpi
Fits the following gearboxes:
BSA M20, M21, B31 and B33 (1948-1959)
BSA A7, A10 with bolt-on gearbox, plunger frame & C11 4-speed
BSA A7, A10, B31, & B33 with STD gearbox
Part numbers: 65-3403, 03-0720, and 02-0452