Manufacturer: Airtech Studios
Type: M-nub Trolley
Compatibility: M4 and Scar Maxx Hop-up chambers
Materials: Ultra-tough polycarbonate
Length: 6mm

Pros:

• Modifications on the slide bars on each side compared to the original. 

• The overall contact area has been extended by 0.5mm compared to the original to cover most hop-up windows.
• Modified Maxx Trolley for most stable performance.
• Fully Increase Accuracy and Consistency.
• Tough Polycarbonate Construction.

Cons:

• Compatible designs:
• MAXX CNC Aluminum Hop-up Chamber ME - PRO & SPORT
• MAXX CNC Aluminum Hop-up Chamber MI - PRO & SPORT
• MAXX CNC Aluminum Hop-up Chamber SV - VFC SCAR-L/H
• MAXX CNC Aluminum Hop-up Chamber ME - Umbrella Armory Ver.
• MAXX CNC Aluminum Hop-up Chamber ME - EMG & Specna Arms Ver

Comments: The TDC (Top Down Centre) Trolley is designed for the Maxx Hop-up chambers to incorporate the use of tensioner nubs specifically for Flat-hop builds (although some R-hop set-ups would work also).  Depending on the tensioner nub of various sizes and brands you tend to use can help on the consistency, accuracy or achieve longer distances for your shots.