FCW L119A2 MWS / GBBR Conversion Kit
 
L119A2 CNC Rail + Barrel Nut with Outer Barrel And Unicron 265 Inner Barrel
L119A2 DE GBB Grip with CTR Stock
KAC300 Style Sight Set
QD Sling Ring, SF Flash Hider, L119A2 Cocking Handle Latch
A single M4 MWS GBBR is all you need to convert it into an L119A2-style GBBR.