The Elite Bike Trainer Adaptor kit makes Elite trainers compatible with bycicles with a variety of rear wheel axle sizes. Two trainer adaptor kits are available; 10mm and 12mm diameter through bolts and 135x10 and 135x12 m . Compatible with home trainers that require a fully assembled bicycle. Not compatible with R.A.T. (rapid axle technology) system, mainly used with Focus frames.