Airsoft Systems is a Bulgarian company that is now making very fine Hop Up Chambers made specifically for all AR15/M16/M4 AEG series. This hop-up chamber doesn't have the detection circuitry but is for people who want to enjoy the solid performance of the hop-up unit designed by Airsoft Systems.
It's made of Shock Resistant Reinforced Technopolymer which all sounds very technical so it has to be good, right? Seriously, it's a tough material that does not bend or crack under pressure. It's optimized for high performance hop up rubbers with precise clicking adjustments so you know you've altered it in some way! As Airsoft Systems likes to remind us, they are Airsoft fanatics too so they've designed this hop-up as much for themselves as for their customers!