The replacable derailleur hanger is secured to the bike's frame using a fastener or fastener. A hanger can use up to 4 fasteners, but most hangers use one or two.
The socket where the rear hub sits when the rear wheel is properly inserted and secured in the frame.
Rear Derailleur Hole
10mm x 1 threaded hole where the rear derailleur is attached to the hanger
Rear Derailleur B-Screw Tab
This tab is an important feature on any hanger and allows for the rear derailleur pulley clearance to be set. The flat side of the tab always faces towards the rear of the bike.