This valve will fit later A+ small bore cylinder heads that use a 1" (25.4mm) exhaust valve, this valve has 3 grooves for the later collets.

Can also be fitted to earlier heads as long as you use the collets to suit the valve.

If you need earlier valves then please look at the following...

Large collet type early exhaust valve AEA434

Single collet type exhaust valve 12A1987