Its well thought out design does not impede the use of the charging handle on M4 type rifles. The one piece design makes it easy to install to any Military Specification flattop upper receiver and the sight is secured to the upper using a slotted fastener which is threaded into a self locking steel thread insert. Machined from 6061 aircraft grade aluminum and Military Specification Hard Coat Anodized, our Fixed Back Up Iron Sight is both lightweight and durable. Features: One Piece Streamline Design A1 Sight Adjustment A2 Aperature Slotted Screws Attachment Light weight Materials & Construction Aircraft Grade 6061-T6 Aluminum Military Specification Type III Hard Coat Anodized 1.7 Ounces! Made in the USA!