On my application I am not using the aluminum outer collars shown, I made some CM steel outer collars up so they could be welded to the existing lower engine cradle. I do have future plans to make an aluminum engine cradle with the mounts integrated into it.
The inner collars are steel with an 8mm inside diameter, I machined these to an inside diameter of 10mm to fit the YZ125 engine mounting bolt diameter. The rubber bushings are a "hard" rubber version for use on BMW alternators, there is also a "softer" version available.
Urethane "Hard" bushings = Bosch part# 1 120 321 002
"Soft" rubber bushings = BMW part# 12 31 1 268 435
Inner collars for the bushings = BMW part# 12 31 1 268 434 or Bosch # 1 120 320 001