This Leupold Quick Release Weaver Style Mount (49866) use an adjustable double-lever mechanism to lock the rings securely into the base. Just simply rotate the levers to achieve a lock. The spring-loaded levers can be "parked" by pulling each lever out, disengaging it from the locking screw. This allows the user to adjust the levers to the desired position. Then, just release the levers back into the spring. It is engineered to retrofit any existing cross-slot base, thus converting existing mount bases into a quick-detach system. However, for the kind of fail-safe, return-to-zero performance that's typical of Leupold Detachable Accuracy Mounts, it is recommended that you team QRW Rings with QRW Bases. The VX-III features the Boone and Crocket Big Game Reticle system. A large selection of reticle including the illuminated reticles make finding the VX-III scope that's right for very easy. The VX-III also has Leupold's Matched Index System for up to 98% light transmission.