PolarStar Gearbox Shim Set for Cylinder Conversion Kits (0.152")

The PolarStar Gearbox Shim Set (0.152") is a precision tuning component designed to secure PolarStar HPA cylinder conversion kits inside AEG gearbox shells. By eliminating unwanted cylinder movement, this shim set helps maintain proper nozzle alignment, consistent air seal, and reliable feeding—critical factors for high-performance HPA builds.

During HPA conversions, gearbox shell pin sizes can vary depending on manufacturer. To ensure universal compatibility, PolarStar cylinder conversion kits are manufactured with pin holes large enough to accept the largest common pin diameters. In some gearboxes with smaller pins, this can allow the cylinder to shift forward or backward during operation. Even minimal movement can negatively affect performance by altering nozzle protrusion and BB seating.

These precision brass shims are designed to take up that excess space and firmly lock the cylinder in place within the gearbox shell. Once installed, the cylinder remains properly positioned throughout the firing cycle, ensuring consistent nozzle extension, improved air seal, and stable shot-to-shot performance.

Manufactured from high-quality brass, the shims offer excellent durability, resistance to deformation, and long-term reliability. Brass is ideal for this application due to its strength and ability to maintain precise tolerances under repeated stress. The 0.152" thickness is one of the most common sizes required for correcting pin tolerance differences in popular gearbox shells.

This shim set is engineered for easy installation and is compatible with most standard AEG gearbox designs, including common Version 2 and Version 3 platforms. No permanent modification is required, making it an ideal solution for both new HPA builds and existing systems experiencing inconsistent performance.

By preventing cylinder movement, the PolarStar Gearbox Shim Set directly improves:

• Nozzle alignment consistency

• BB seating reliability

• Air seal efficiency

• FPS stability

• Overall accuracy and efficiency

The shims are fully compatible with all PolarStar cylinder conversion kits, including:

• PolarStar F2

• PolarStar F1

• PolarStar JACK

• PolarStar Kythera

For HPA users, techs, and competitive players, this shim set is an essential tuning component. It protects your HPA investment and ensures your engine operates exactly as intended inside the gearbox shell. If you’re aiming for maximum consistency, reliability, and performance from your PolarStar setup, the 0.152" Gearbox Shim Set is a small but critical upgrade that delivers measurable results.

Manufacturer: PolarStar