PolarStar Kythera® SA Nozzle (Type: #13) — Precision Drop-In Nozzle for Kythera HPA Engines

When precision, reliability, and exact fitment matter, the PolarStar Kythera® SA Nozzle (Type: #13) delivers. Engineered as a drop-in nozzle for PolarStar Kythera HPA engines, this brass nozzle is a purpose-built component that helps ensure consistent sealing, smooth cycling, and excellent shot-to-shot performance in a wide range of replicas. If you’re building or tuning an HPA system, the correct nozzle is one of the small parts that makes a big difference — and the #13 Kythera nozzle is made to get that fit right.

Machined Brass Construction for Durability and Seal Integrity

Manufactured from high-quality brass, the #13 nozzle offers a robust balance of toughness and dimensional stability. Brass resists wear, maintains tight tolerances over thousands of cycles, and provides a smooth, low-friction mating surface with internal engine components. That means fewer leaks, crisper cycling, and improved longevity compared to softer or poorly machined alternatives.

True Drop-In Compatibility with Kythera HPA Engines

This nozzle is designed specifically for PolarStar Kythera HPA engines as a drop-in replacement — no heavy modification required. Install it directly into your Kythera engine to match nozzle length to your replica’s cylinder and hop-up geometry. For builders moving between cylinder conversion systems or swapping engines, using the correctly numbered nozzle keeps setup predictable and repeatable.

Why the Numbered Nozzle System Matters

PolarStar uses a numbered nozzle system (rather than only rifle model names) because nozzle length and fit can vary even between the same replica models made by different manufacturers. Small differences in receiver thickness, gearbox shell design, or barrel/hopup placement can alter the nozzle length required for a perfect seal. Selecting a nozzle by number — in this case #13 — ensures you get the length that best matches the measured requirements of your replica’s cylinder-to-hopup distance.

A few practical notes about PolarStar’s system you should know:

• The number printed on each nozzle corresponds to a measured, repeatable length that PolarStar has mapped to many common replicas.

• The numbered system is universal across compatible engines: once you determine your replica uses a #13 nozzle, that same number will be correct for Kythera, F2, or other numbered-nozzle engines.

• Some Kythera engines built for non-standard cylinders (models made specifically for a certain replica like A&K/JG SR-25) use a “K”-prefixed nozzle because they employ different cylinder dimensions. Those K-nozzles share design profiles with numbered nozzles but are intended for those unique cylinders.

• The #1 nozzle is produced in very high volumes and is typically left unmarked to optimize production; every other nozzle carries its number for easy identification.

Ideal Use Cases

• You’re installing a Kythera HPA engine into a replica and need the correct nozzle length for reliable feeding and sealing.

• You’ve measured your replica’s required nozzle length (or referenced PolarStar’s compatibility list) and confirmed #13 is the match.

• You want a durable, low-wear brass nozzle to improve long-term performance and reduce maintenance headaches.

Quick Installation Tips

1. Confirm your replica’s measured cylinder-to-hopup distance or consult PolarStar’s compatibility list to verify #13 is the correct length.

2. Install the nozzle into the Kythera engine per PolarStar instructions — the part is designed as a drop-in item for Kythera systems.

3. After installation, run a brief function test and verify sealing and cycling at low pressure before returning to full operational settings.

Specs & Manufacturer

• Type: Kythera® SA Nozzle, #13

• Material: Brass

• Fitment: Drop-in for PolarStar Kythera HPA engines (numbered-nozzle compatible systems)

• Manufacturer: PolarStar

Small details deliver big results in HPA systems — choosing the correct nozzle length and a precision-machined material like brass can greatly improve consistency, reliability, and longevity. If your replica requires a #13 nozzle, the PolarStar Kythera® SA Nozzle (#13) is the reliable, professional-grade choice to keep your Kythera engine sealing and cycling like a champion.