Rearden was founded with a simple mission: be great and innovate. They have never been one to back down from a challenge or say something can't be done. Can't is not a part of their vocabulary. If you want it bad enough, there is a way. It may cost more, it may take more time, it may even have to wait for the technology to catch up to the idea. But, everything is possible. These fit the plan B type mounts. This is an updated version that has larger wrench flats on the rear. Always use an alignment rod to ensure that the entire system is set up correctly. Make sure all surfaces are cleaned and the muzzle device has been torqued and Rocksett to the barrel. Use on a Q can voids your warranty, be warned.