Magpul MBUS Magpul Back Up Front Sight Gen2 - A color injection molded folding backup sight is essential when using optics. If your optics fail, make sure you have a second option. The MBUS attaches to 1913 style Picatinny rails. Made in USA. Impact resistant polymerSpring loaded flip-up sightMounts to MIL-STD-1913 Picatinny and NATO STANAG 494 railsMounting hardware includedWeight: 1.3 oz.Length: 4.70 in.Height above rail stowed: 0.51 in.