Retro Arms CNC SOPMOD M4 NGRS Gearbox 8mm pre build all will be smooth without

all will be smooth without the risk of snagging on your environment

Bottom of page will contain gearboxes tested

Build Specs ect

buffer tube

Upper and Lower

Retro Arms CNC SOPMOD M4 NGRS Gearbox 8mm pre build all will be smooth withoutRetro Arms CNC gearbox for TM NGRS SOPMOD M4 AEG. When it comes to building a reliable high tier NGRS, this gearbox should be your first item in your build. With the stress of recoil, you need to have the strongest gearbox possible. Precision machined from a block of billet EN AW 7075 T651 aluminum Durable anodized finish Reinforcement in key stress points to counter rapid wear from high performance parts Pre radiused cylinder windows helps evenly