Silent Industries AEG M4 Alpha Hop-Up ChamberLET US SHOW YOU THE MOST FEATURE PACKED AEG HOP UP EVER MADE! TRUE TDC To get the most consistent pressure on the bucking through the hop up settings, we had to include TDC. This means the nub can only move in up & down motion. The TDC trolley we include is made for nubs, so you can use your desired nub. We recommend using our Black Nubs, Blue Nubs, ML Omega or similar height nubs, because our system was optimised for it. Our TDC system provides the