Snipertools has released the Angle Cosine Level or “ACL”. The level attaches to any rifle and provides both tilt and cant indication. Cant is indicated in degrees in bolt numbering to facilitate quick mental math and releasing the shot to hit on-target.
Description from SniperTools:
The “Angle Cosine Level,” (ACL) has an “Anti-Cant’ device incorporated into it. Opened with a flip of your thumb the all mechanical anti-cant device is displayed in full view and also rotates so that it remains vertical on the Z axis. This device is not a spirit bubble level. There is no glass vial to break and no liquid to leak out or freeze from cold weather temperatures. The ACL is impervious to the elements, completely mechanical, rugged and accurate!