Bios driver meaning-Compatible with JinMing Gen8 J8 M4A1.-Upgrade material,more sturdy and durable. Color: Black. Material: Metal/Strong Nylon Package Include: 1x Metal Buffer Tube-Black(Gen8)+ FAB Nylon Stock Items will be dispatched within 24 hours (excluding weekends and public holidays)after full payment has been received as cleared funds. Specialist services dubaiBrand: Jin Ming (JM) Metal Top Rail for JM Gen.8 M4A1 Receiver Shell. Metal Top Rail for JM Gen.8 Receiver Shell. Standard 22mm picatinny rail. Enable you to mount heavier optics and picatinny rail accessories.Fits the plastic receiver shells. Requires modification to fit on nylon receiver shells.. USD7.50. Add to Cart.