Saris MTR 2-Bike Add-On Black. Whether youve invited more friends for an epic ride or cant decide which rig to take to the trails the MTR Add-Ons have you covered. Compatible with both the MTR 1-bike and 2-bike hitch rack these add-on trays save you the hassle of buying a new rack to haul more bikes. Built with the same robust materials as the MTR rack these add-on trays are ready to roll out of the box and are the soul of the Modular Tray Rack (MTR) functionality.