Maxx Model CNC ALUMINUM Hop up Chamber M4A PRO Echo 1 Airsoft Guns BLT M 005 VSR BLT M 005 VSR There is a see through channel below the rail to keep the mount lighter and for some firearm types except KWA) Standard 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 5mm and OD12mm are sold separately) Mounted the removable CNC Brass Side Wings to slide smoothly into the outer barrel slots Included an advanced CNC Delrin Locking C Clip to hold the inner barrel tight in place without wobbling and twisting Equipped with 2 compression springs on top and center to ensure the hopup unit is seated straight and air tight during use Specially designed with a new BB Latching System to prevent BB dropping after removing the magazine The Latching Arm can also be manually pressed to release the remaining BB from inside the hopup chamber Compatible with any 11mm inner bore AEG Gearbox HPA Engine nozzle outlets The Dual UV LED Tracer Module to glow BB in the dark ready