Brake Rotor Bolt (DIN 912 M8 x 20)

This is a generic screw for holding the rear brake rotor to the hub adapter.

M8 x 1.25 thread pitch, 20 mm long. Class 12.9. Zinc-plated steel.

Takes a 6 mm socket driver (Allen key). 

Used to attach the rear brake rotor to the hub adapter. Torque spec is 30 Nm (22 ft-lb). Definitely apply medium-strength thread locking agent prior to assembly.

You'll need 5 if you want to replace all of them.

Or you can get the fancier factory bolts with "Precote 85". (Factory bolts are Class 10.9, which arguably means they stretch more, giving them better vibration-resistance, but that's probably an engineer's splitting hairs, so I wouldn't hesitate to use these stiffer generic screws on my own or any customer's bike.)