The C8 Short Collar was designed to work with the C8 and L119A2 series of CanSOF rifles. Most people use the CanSOF C8 Collar to mount a B-Mount Suppressor (AEM2, AEM3, AEM4) to a 11.5″ FSB upper.
Like many other collar systems, the C8 Collar was designed for a specific barrel profile. It wont fit over any random barrel. Click here for instructions on how to prepare your barrel to accept the C8 Collar.