Small Wheel Adapter for Universal Wheel Holders
Do not use any 24" - 29"/700c diameter wheel bikes. Doing so will void the warranty.
Please note: The Small Wheel Adapter is for the rear wheel only of a 20" fat tire bike, to prevent derailleur hanger interference. But, 20" fat tires can be mounted without the adapter, you just need to shift the rear derailleur into the lowest gear (the largest cog in the back) before you put your bike on the rack, doing so will pull the derailleur towards the rear wheel, i.e. away from the wheel holder cradle and therefore the adapter would not be necessary. But, you would have to do that every time you load that bicycle which is why most people end up using the Small Wheel Adapter.