This is a brand new, replacement kicker cotter pin that holds your kicker arm to the kicker shaft on your Triumph or BSA engine. This is an oversize cotter pin and includes the nut. You drive out your old one with a soft drift and if it is no good, you can use one of these replacements. If your cotter pin has been beat in and out of your motor a million times your hole may be enlarged, no longer giving a secure fit with the tapered pin. That, my friend, is why you need one of these handy oversize kick start cotter pins. Oversized replacement for OEM # 57-4356, 57-1222, 02-2579