The Knight's Armament Corp. Upper Receiver Extending (URX) Rail system is one of the most trust tactical free floating rails on the market, given that KAC invented the railed fore-end in the early 90s.
Using a proprietary barrel nut, the URX II and III feature a slick design which requires specialized tools for installation, but yields one of the lowest profile rail profiles available.
This rail is 12.5" long, and features a built in front sight! This makes it one of the best values in the rail market, as well as one of the slickest! with 12.5" of length to work with, this rail system is well suited for full sized carbines and rifles.