SOLD The hop rubber and hop unit need to be replaced. I have included a picture of it. An easy replacement can be found here - https://samoon.com.tw/m4-kit-04?search=hop%20up GHK M4 with Z-Parts short Steel Barrel and URGI rail. This is a gen 1 GHK M4 with a magnetic bolt catch and high flow nozzle. Shoots well and hop up is zeroed to 65 yards. Barrel and hop up unit were replaced earlier this year with stock GHK unit. Added anti walk retention pins. Comes with 4 mags. There is some cosmetic damage on the inside of the lower in the magwell and on the barrel nut but this does not impact function. Comes with basic A2 stock not B5 stock and does not include light, BUIS, and foregrip.