TreeFrog's new universal Fork Mount Base - here the model that fits their RoundBar holder..

The Fork Mount Base is compatible with a multitude of different axles/adapters from TreeFrog, so you can set it up to fit exactly the bike(s) you want to transport on your RoundBar rack. These are purchased separately on the side depending on which front fork mount you have on your bike.

A rear wheel holder is included, which is compatible with all types of tires.

NOTE: The Fork Mount Base comes without axles/adapters - pictures for illustration only. These must be purchased separately, depending on what fits your bike.