1215KM (1/2 x 28)is our latest offering in the Dead Air sound suppressor mounts line. Threaded for 1/2 x 28, 1215KM is a Keymo compatible brake, compatible with all Dead Air 223 caliber sound suppressors. We don't like brakes for 223 ARs, they're loud and obnoxious, and it's our opinion an AR has low enough recoil, a brake is wholly unnecessary. While a brake will reduce felt recoil, it has unjustifiable compromises in increased concussion, noise and flash signature, one also wouldn't want to use a brake from inside a vehicle or indoors, these are trade offs a flash suppressor doesn't have. That said, a brake for a sound suppressor does have its use as a sacrificial first baffle to increase the longevity of a sound suppressor. For this reason, there won't be a 1215 (sans the Dead Air Keymo mount), 1215 design will solely reside on 1215KM (1/2x28) and 1210KM (5/8x24). 1215KM is a single chamber brake, with a baffle like chamber forward of the ports (dear ATF, this does nothing to reduce the decibel). The tines on top and bottom that connect the Keymo mount to the front chamber are of symmetrical, we think a smaller/thinner top tine to force more gas upward is unnecessary. Let's do away with ambiguities and insinuations as to what it is and what it does, 1215KM is a brake, it'll be loud, and its concussion will kick up dust visible from the next county if you shoot it from a prone position without a sound suppressor. 1215KM is meant to be used with a Dead Air sound suppressor attached. 1215KM is designed to have less concussion than most brakes. In terms of felt recoil reduction, most brakes are similar in performance. In the old days, some tank guns brakes are nothing more elaborate than a tube mounted perpendicular to the bore forming a T shape, it doesn't take much to make a brake that works. If one is to look at old tank gun brakes, he will soon realize these tank gun brakes and most muzzle brakes for small arms today bear surprising resemblances and design. To make a brake less offensive is far more difficult. In our experience, Knight's Armament's MAM brake is probably the best in that category, it's also very costly. 1215KM follows our design philosophy, it's a simple and effective brake. It does what it's designed to do, and does so without making unsubstantiated claims. We tested the 1215KM against a host of brakes and flash suppressors. Flash suppressors are the least concussive. The one we know to be the most offensive was as loud, concussive and obnoxious as ever. Nothing we don't already know. The real surprise is 1215KM's performance. To wit, even though the Mk12 brake is the 1215KM's inspiration, it is still an FCD design, we did not use most of the Mk12 brake's features. The attributes that helped 1215KM even LESS concussive: 30 cal exit hole (we opted to follow Dead Air's example, instead of making it more 223 based). The ports are not angled like the Mk12 brake. The larger bore size makes for a less effective brake, but it's .223 we're talking about that doesn't even need a brake to begin with, but it does have significant impact on noise and concussion. The flat sides of the port don't direct gas back to the user, or bystanders behind the shooter. 1215KM's design goals were not only met, but exceeded. Machined in 4140 steel, heat treated and black nitrided. 1/2x28 Length: 2.402" Weight: 3.81 oz Proudly designed and made in the USA.