Unless you're attaching your Magura brake to a 160mm post mount on your fork, you'll need a Quick Mount Adapter, known by the initialism QM. Magura decided with the proliferation of choices available to riders, it makes the most sense to provide the brakes without brackets and have the customer choose the right bracket(s). Below you'll find a guide to determine which is right for you. Happy hunting and safe stopping.

QM5 bracket — 203mm rotor, front IS mount
QM7 bracket — 203mm rotor, front post mount, two-piston
QM8 bracket — 203mm rotor, RockShox BoXXer
QM9 bracket — 203mm rotor, rear IS mount
QM10 bracket — 180mm rotor, rear IS mount, two-piston
QM11 bracket — 160mm rotor, front IS mount or 203mm rotor, front IS 203mm mounts, FOX 40
QM12 bracket — 180mm rotor, front IS mount or 160mm rotor, rear IS mount
QM20 bracket — Replaced by QM40
QM40 bracket — 180mm rotor, post mount
QM41 bracket — 180mm, rear IS mount, four-piston
QM42 bracket — 203mm, post mount, four-piston