Legacy Bear Models:  Model 80-200: 30 mm shaft (slight additional charge for this shaft size only). NOTE: 80-200 may require the use of a longer threaded shaft depending on style of wheel being mounted.

 Model 80-303: 40 mm shaft

Recent Production Bear Balancers:

Years 2003- Early 2006: 36mm shaft (must be special ordered)

Years Late 2006 - July 2009: 40mm shaft.

Cartek Balancers: 

Mid-2009 to present:  40mm shaft.