[Tikkasharpshooter]

Alex, Did you try to discuss this with the vendor or the manufacturer?  Were they helpful and/or try to give you full refund before you start trashing them on the forum?

[Tikkasharpshooter]

I have two Clamp-on muzzle brakes from Coretac solutions and couldn't be happier  :).
Their quality is excellent and fit and finish top notch.  The Clamp-on ordering can be more user friendly but it works.  You need to provide precise dim during the ordering.
A friend of mine recently did a review on Canadian Gunnutz: http://www.canadiangunnutz.com/forum/showthread.php/950154-Review-Coretac-Solutions-Clamp-on-Muzzle-Brake?highlight=coretac

Hope this helps.