The SPR collar is the traditional collar system for Mk12s. They have an internal step that interfaces with a step in Mk12 barrels that prevents rearward movement. The set screw, typically positioned on the bottom prevents rotation. Here are the different SPR collar options:

Long – This was designed for use on Mk12 Mod 1 and Mod H rifles and will work on any properly profiled Mk12 barrel.

Short – This was designed for use on the Mk12 Mod 0. This will work on any properly profiled Mk12 barrel. It functions the same as the SPR Long collar but is shorter to prevent interfering with the Mod 0 FSB.

Daniel Defense – This was designed for use on legacy Daniel Defense Mk12 barrels (pre 5/9/2022). To determine if this collar will work with your DD barrel measure the distance from the bare muzzle to the SPR step. If it is 2.3″ use the SPR DD collar. If it is 2.4″ use the SPR Long collar.

B-Mount – This was designed to convert your Mk12 barrel to accept B-Mount suppressors (AEM2, AEM3, and AEM4). This will work on any properly profiled Mk12 barrel.

Blank – This was designed to allow a gunsmith to fit a SPR collar on a non-Mk12 barrel. This will require a gunsmith to also profile your barrel, but this is a prefered option if your barrel is too thin to be re-profiled to match a Mk12. Click here to find the barrel prints.