The MHS 1+1 Receiver Base is essentially the base unit to start building out your Saris bike rack, compatible with both the DUO Tray and the DUO Add-On (sold separately). It's intended to be used with one DUO Tray and one DUO Add-On for a 2 bike capacity, but can also just be used with one DUO Tray. Saris offers DUO Trays rated for either 35lb or 60lb, meaning you can use this system both for standard mountain bikes and e-MTB's. Once built out, the MHS Rack offers features like a tilting mechanism for easy cargo access, and integrated locks for post-ride bevies at the brewery.