What makes this lower different than its counterparts? The answer is simplea | the KE Arms KP-15 is a monolithic polymer AR-15 style lower receiver made from injection molded, 30% glass-filled nylon. Its unique design incorporates the buffer tube, pistol grip, trigger and a 13-inch (LOP) buttstock into the receiver as integral components. The result is an affordably priced, lightweight lower receiver. This complete model includes the KE Arms DMR Trigger, with 4.5lbs pull. The KE Arms KP-15 lower receiver uses a carbine buffer and spring. The take down and pivot pins have built-in detents, which increases durability by eliminating the spring and detent holes. The buffer detent ( Mfg: Ke Arms