V2 Hop-up Thing Gearbox Lip

Hop Up Thing — Gearbox Lips

Stop midcap syndrome before it starts.

If your shot groupings fall apart mid-magazine or your output velocity fluctuates between mags, your nozzle is probably deflecting inside the hop up. A properly fitted gearbox lip eliminates that movement by supporting the nozzle from below, keeping everything centered and consistent on every single shot.

These alternative gearbox lips are drop-in replacements for the stock lip that comes with the PolarStar Hop Up Thing. All three share the same outer diameter of 0.440 inches but offer different inner diameters to match your specific nozzle. Tighter clearance means less room for the nozzle to move, which means more consistent loading, more consistent hop, and tighter groups.

Which one do you need?

Measure the widest point of your nozzle diameter, then select the gearbox lip with an inner diameter just larger than your measurement. For example a 0.280 inch nozzle takes the 0.285 inch lip.

Stock Gray — 0.305" ID
Comes included with every Hop Up Thing. Best for AEG nozzles which tend to be wider toward the rear. Maximum clearance for compatibility across the widest range of setups.

Black — 0.285" ID
Designed for the Fusion Engine and Kythera. Leaves only 0.0025 inches of clearance on each side of the nozzle for near-zero deflection.

Silver — 0.275" ID
Designed for the JACK and F2. Same ultra-tight 0.0025 inch clearance on each side. The right fit for PolarStar's most popular engines.

Important note: These lips address nozzle deflection, not nozzle misalignment. If your nozzle is misaligned with the bore that is a gearbox positioning issue and will need to be corrected separately using traditional alignment methods. With proper alignment already dialed in and the correct lip installed, midcap syndrome is effectively eliminated.

Compatible with PolarStar HPA systems and AEG setups. Works with other HPA platforms as well.