Semroc Centering Rings Fiber BT-20 to BT-60(2pk) SEM-RA-20-60
Laser-cut rings for centering a BT-20 tube inside a BT-60 tube
I.D = 0.736
O.D = 1.6
These centering rings are nothing fancy, but they do the job! You can save money because you don't have to buy a complete motor mount kit.