- Prevents HPA cylinder movement
- Improves nozzle alignment and air seal
- Compatible with all PolarStar engines
These precision shim sets are designed to secure an HPA cylinder firmly within the gearbox shell, preventing unwanted forward or backward movement during operation. Small variations in gearbox pin diameter between manufacturers mean cylinder conversion kits must allow enough clearance to fit the largest pins, which can sometimes result in movement when installed in gearboxes with smaller pins.
If the cylinder can shift under use, nozzle alignment can change, affecting how consistently BBs are seated into the hop unit. This can lead to reduced air seal, inconsistent FPS, and overall performance loss. By correctly spacing the cylinder to match your gearbox pin size, these shims help maintain proper nozzle position and consistent air delivery.
Available in multiple thicknesses to suit the most common gearbox pin diameters, these shim sets allow a more precise and secure fit across a wide range of replicas. They are fully compatible with all PolarStar cylinder conversion systems, including F2, F1, JACK, and Kythera engines. Read the full description for size compatibility.
Fast Delivery
Delivery & Postage
Here at Patrol Base, we send all our packages from our Warehouse based in the UK with the exception of European Warehouse Items. All of our parcels are sent with specially picked couriers to ensure your parcels get to you on time and in one piece.
For more information please check out our Delivery Information Page.
Estimates
Below are some rough postage prices for orders. Please note these are subject to change and are only a rough guide. For a more accurate postage estimate please use the Postage Calculator at the basket.
UK 3-5 day Standard
£6.95
From
Dispatched with 24hr UK mainland
£8.95
From
Highlands / Islands
£24.99*
From
* Please note that Scottish Highlands, and Islands postage prices can vary wildly. Please refer to the Postage Calculator at the basket for the lowest possible price.
Returns
We want you to be absolutely happy with our products and services, so we provide the simple Patrol Base guarantee: if on receiving your item you are unhappy with your item for any reason then simply send it back to us. We will replace or refund the item.
You can return any item for any reason whatsoever, even if you have just changed your mind, within 14 days of receipt of the order. This is in addition to your rights under the Consumer Protection (Distance Selling) Regulations 2000.
For more information on returning products, and how to do it please visit our Returns Policy Page.
Description
Shim Size Compatibility Guide
0.157 inch
Best suited for VFC, Tokyo Marui, E&L, and JG gearboxes
0.152 inch
Best suited for Ares, CYMA, G&G, ICS, and Dytac gearboxes
Features
- Brass construction
- Compatible with all PolarStar HPA engines
- Ensure your cylinder sits correctly
- Improves Air seal, more consistent FPS and overall performance
- 2 Sizes available - Compatible with most Airsoft brands
Package Includes
- PolarStar Airsoft Gearbox Shim set for Cylinder Conversion Kits
Specification
General
Parts & Accessories Type | Internal Parts |
|---|---|
Internal Part Type | Shims |
 | Custom Parts Upgrade Parts Use of HPA is considered a "modification" and is not covered by your warranty. |
Name Variant | 0.152", 0.157", |
Construction
Internal Part Construction | Brass |
|---|
Part Specific
Part for Power Source Type | HPA |
|---|---|
Package Includes | Shim Set |
Size guide
Parts Fitting
Upgrades and Downgrades should only be undertaken by experienced players, or Airsoft Technicians. Please note, changing any internal parts of a weapon voids its warranty unless done in-house by our staff.
Please ensure that when fitting parts the part purchased is the correct part, as once a part has been fitted we cannot accept return.
We do know that players love to tinker, so we're here to give you help should you require it, and if needed you can get in touch with our workshop for more help!
Unique Parts
Please note that some parts may be unique to a specific brand of weapon. For example: Parts for an ASG M4A1 may not fit an ICS M4A1.
Parts from the same brand typically have a high chance of fitting, though be warned, some replicas use unique parts, so please ensure the part will fit before you attempt to fit it.
If you require help with fitting any parts feel free to get in touch with us via our Contact Us Page.
For more information with fitting parts, or should you require help, feel free to get in touch with our Workshop Department via our Contact Us Page.
Terms and Conditions relating to parts fitting can be read on our Terms and Conditions Page.