The rings are included as a catch all for other applications. Ross, when he owned QuickTime, prior to selling quicktime had these pre-packaged with the required hardware to fit other transmissions that had bearing retainers smaller than the TKO. I believe its the T10 and the New Process 833. It's just extra parts and it created a bunch of phone calls. By the way, the tolerance on the bore should not be sloppy. The Tremec needs .005 TIR when dial indicating.

Tony
Hurst Drivelines