ULTIMATE Ultimate Metal Hop-Up Unit - M4/M16
- A full metal hop-up unit from Ultimate.
- Features an innovative o-ring that improves the seal between the front of the gearbox and the hop-up unit.
- The adjustment mechanism must be assembled by the user and offers a nice tight adjustment once fully assembled.
- Maintains the hop-up setting extremely well.
- Suitable for all M4 variants with standard hop-up units.