The Rev Rack Tent works with the Thule Caprock XXL for sleeping,  and for transport only, you can mount the closed Rev Tent on all sizes.  

If you'd like to sleep on the roof and have a S,M,or L size Thule Caprock, you would need the Rev Roof Top Tent.  

The Rev Roof Top Tent's Platform X can be mounted to the Thule Caprock with the included mounting hardware.