These would be the hottest detachable iron sights on the market, if they were made of iron! The Magpul Back-Up Sight or MBUS, is Magpul's foray into the the folding, detachable sight market and easily one of the best. The MBUS easily attaches to any flat top weapon with a standard weaver rail and is meant to provide a fold away. back up option to your primary optic sight. high quality, official magpul product.