SELF TIMING "muzzle brake compensator" (MBC) A007 is unique and patent pending. The A007 is a "self timing" MBC which require you to drill a small hole in your selected thread sleeve with the supplied drill bit. You can then take MBC off, fit a moderator, then refit MBC with it perfectly centered every time, as you dont have to worry about a degrading crush washer. This MBC will enhance accuracy by reducing muzzle flip for target shooting and hunting. And it looks so cool on. select which thread and colour you want'; 1) 1/2x20 matt black 2) 1/2x20 raw silver 3) 1/2x28 matt black 4) 1/2x28 raw silver MBC model; A007 calibres; .17 .22LR, .22 magnum material; aluminium weight; 37gm overall length; 50mm top compensator ports; 6 vertical and 2 angled forward side brake ports; 3 larger each side included; stainless steel grub screw, alen tool, drill bit. Designed and made in New Zealand Support NZ made. Please note: Instructions will be given to fit this, so all you need is basic home handyman skills and a drill to drill a 2mm deep hole in the supplied thread sleeve.