M2 Armament Group DIY Polymer80 PF940CV1 Rail Set w/ Locking Block/ Rear Rail Module/ 2x Pins Black. Engineered specifically for the growing community of home gunsmiths 80percent builders and 3D printing enthusiasts (3DP / FMDA / PY2F) this essential steel rail kit delivers the critical structural components required for smooth slide cycling rigid lockup and flawless frame function. Specifications for M2 Armament Group DIY Polymer80 PF940CV1 Rail Set w/ Locking Block/ Rear Rail Module/ 2x Pins: Manufacturer: M2 Armament Group Color: Black Package Contents: M2 Armament Group DIY Polymer80 PF940CV1 Rail Set w/ Locking Block/ Rear Rail Module/ 2x Pins M2 Armament Group M2-UPPER-C-BX-16: DIY Polymer80 PF940CV1 Rail Set w/ Locking Block/ Rear Rail Module/ 2x Pins Black