Hepco & Becker's new Smartrack system offers modular pieces allowing you to fit all BASIC tank and rear bags onto your rack. This kit includes both the Smartrack mounting piece as well as the counterplate mounting piece that attaches to your rear bag. If you are mounting a Street Daypack, Royster Daypack, or Epic 3 or 6 bag you will need this kit.
If you are retrofitting a case with a counterplate mounting plate already attached then you just need the smartrack piece found HERE.