Good morning Shaun, I have just measured my bellows and it's 22mm on the shaft end so I guess that's correct as I have fitted one without any problems. The peening is just a matter of lots of tapping round and round with a small hammer, two things to be careful off. 1. Keep the joint fully compressed ALL OF TIME whilst peening, this is difficult, I held it in a large vice. 2. Protect the shaft from wayward hammer blows which will cause damage, I held a small piece of 3/5mm steel against the shaft as protection. I hope this all makes sense, i am not known for my grammar Guy