The WORKHORSE M-LOK compatible rail system was designed to be a lightweight and slimline option to be used on MIL-SPEC carbines available on the market today. With M-LOK mounting options at the 3.6, and 9 o'clock positions and skeletonized areas where M-LOK is not used. We still maintain 1913 MIL-SPEC Picatinny rail at the 12 o'clock position that we "notch cut" to match the upper receiver and reduce weight again. Offered in multiple lengths to accommodate different barrel lengths and different needs.