The NEW AAC 90T Ratchet Taper Muzzle Brake mounts are for the SR-7 and SR-5 suppressor line. All AAC Blackout muzzle brakes are machined from high strength aerospace steel alloy and coated in a hard durable corrosion resistant SCARmor finish.Not compatible with the older spring mount (18-Tooth) or ratchet mount (51-Tooth) sound suppressors.