My Grobet keyed chuck hand piece fits the Foredom and my Foredom keyed chuck hand piece, quick change hand piece and the hammer hand piece all fit the Grobet. Although that could possibly be because I replaced the Grobet flex shaft (inner piece, whatever it’s called) with a Foredom one several ago. And my Pepetools sander fits both.
It is so hard to type this much on my cell phone in the waiting room of the doctors office!