Bike frame must have large flat surface dropout to drill a hole or use dropout eyelet/pannier hole(s) to mount rear rack/kick stand for direct bolt-on installation. 145mm and 170mm is the adjuster bar length (the color tube without fish eye bolt at both end). Measures 10" straight line from brake boss/post (at seat stay) to the axle mount center at dropout would use 145mm adapter kit. For larger frame or large wheel measure 11" and up would use 170mm adapter kit.
Attachments are photos of the installation diagram and sample photos of the actual disc brake adapter kits mounted on frame. Please note this item works with 160mm, 180mm, and 203mm caliper w/ bracket (if you want to get 180mm and 203mm rotor please make sure it would clear the chain stay since some bikes has narrow chain stays). It may not fit some bikes w/ rear suspension due to the rear seat stays design are not standard (round tube shape). The adapter kit does not work for "breezer" style dropouts, weight saving dropout (eg. Specialized FSR, Trek Y, GT-i2K which has no additional metal and no dropout eyelet/pannier hole), and not for most Klein bikes. Also note the adapter plate mounts outside of the dropout so you will need to use the QR skewer that included in the package (no clearance issue with rotor/hub). If the adapter plate pre-drilled hole does not align with the dropout eyelet or pannier hole then custom drill new hole on adapter plate is required then secure a bolt though the adapter plate to the dropout eyelet/pannier hole threads (please see our customer's bike sample photo with green adapter kit). Hardware included bolts to secure the adapter plate and adjuster bar and washers to align the adapter/caliper to rotor. Custom mount such as welding may work but we don't recommend it and must consult with bike frame builder/weld specialist first.
Drill hole on adapter plate and bolt-on to dropout eyelet/pannier hole if pre-drilled hole on adapter plate does not align