B&T Officially Licensed USW Conversion Kit for G Series GBB Airsoft Pistols (Color: Black) HPA JACK™ still retains the same SSAC LiquidSpeed JACK™ still retains the same performance and quality you have come to expect from PolarStar products and durability Performed accurately and consistently on ICS CXP CS4 EBB (include old models) M4 M16 AEG series Precision Rotary Dial Knob for fine hopup adjustments Re engineered the precision Hopup Lever and 4mm Bucking Nubs (6mm Bucking Nubs are optional) to perform best with R Hop and Standard Hop to keep the BB shooting accurately and consistently on every single shot Removable Steel Pivot Pin for ease of setup and maintenance Accepted 21 Upgrades your ordinary Glock to a micro SMG for better ergonomics and other 20mm picatinny accessories