Quick-release skewers (abbreviated QR) hold the bicycle wheels in the decoupler. They have a lever that allows the wheel to be quickly removed when we open it, without the need for additional tools. They use a cam mechanism at the lever end to pull the threaded nut at the other end. The cam mechanism can be internal or external; the latter type is cheaper to produce and usually lighter, but it produces a lower clamping force under the same hand pressure on the QR lever.
Wheels with disc brakes can be fixed by QR or thru-axles. Disc brakes generate a lot of torque at the hub. Some bicycle experts argue that disc brakes can eject the wheel from the dropout. For this reason, most disc brake bikes and wheels now use a cartridge axle.
If the quick release is to be replaced, you may need to be aware of the length of the rear QR. Mountain bike hubs for quick release have a length of 135 mm on the locking nut, while road hubs have a length of 130 mm. If the QR is road specific, it may be listed as 130 mm. MTB QRs can be used on road rear hubs. It will have a little extra axle protrusion, but this will not interfere with anything. If the QR is simply listed as “rear”, it may be suitable for the MTB. front road and the MTB QR is 100 mm long.