All these are case boring tools. XR75/80/100, KLX/Zonger/YX, and CRF50 type.
Whipped them up a couple years ago. Have an offset-bore CRF one to make 57mm bore with skirted jug for 138cc upgrade from 124's, too.
Don't get me started on matiFRauD and his copy of the tool he thanklessly borrowed from me for two months, and his Chinese fancy version... What a joke. He showed them mine, built his own, wrong, and is having the hi-style versions built. Bless his heart. Karma owes that ******* a good one...