Prometheus Non-Linear Upgrade Spring for Airsoft AEGs (Model: MS120 / Emerald)

Enhance your AEG’s performance with the Prometheus MS120 Non-Linear Upgrade Spring, designed to deliver consistent velocity and reliability on the field. Manufactured by Prometheus, a division of Laylax and a trusted name in precision airsoft engineering, this spring is built from high-quality spring steel and engineered for advanced performance. Whether you’re preparing for MilSim events or optimizing your build for long-range engagements, this spring gives your rifle the edge it needs.

The MS120 spring is named using a meter-per-second system, which means “120” corresponds to approximately 120 meters per second—or about 400 FPS when firing 0.20g BBs. This allows quick reference for those who build or tune multiple guns, making it easier to select the right level of power for your needs. With this spring installed, you’ll see increased muzzle velocity suitable for outdoor play, long-range shooting, and DMR-style setups.

What makes the Prometheus MS120 stand out is its non-linear coil design. Unlike linear springs that apply a constant rate of force, non-linear springs gradually increase resistance as they compress. This results in a smoother and more consistent power delivery across the piston stroke. The gradual compression helps reduce sudden stress on the gearbox and can extend the life of internal components, especially in high-performance AEG builds. It also leads to a more stable FPS range shot after shot, which is essential for accuracy.

Durability is another key strength of this upgrade. Made from premium-grade spring steel, the MS120 is built to endure high rates of fire and intense gameplay. Whether you’re running a standard build or a heavily upgraded gearbox, this spring is made to last. It’s also color-coded in a vibrant emerald green for easy identification in your parts bin or gear bag—even if you lose the original packaging.

Installation is simple for anyone familiar with Tokyo Marui-spec AEG gearboxes. This spring is compatible with most standard TM-style internals, including those used by popular brands like EMG, Matrix, Classic Army, and others. The dimensions are standardized for drop-in fitment, and with proper gearbox tuning and alignment, you can expect optimal performance without extensive modification.

Keep in mind that while the MS120 is rated for approximately 400 FPS, actual velocity results may vary depending on your specific setup. Factors like air seal, barrel length, cylinder volume, and hop-up alignment all contribute to final performance. For best results, combine this spring with a high-quality air seal and compression system. And, as with any gearbox work, proper shimming and lubrication are recommended during installation.

Key Features:

• Approximate velocity: 400 FPS with 0.20g BBs

• Non-linear design for smoother, more reliable power delivery

• High-quality spring steel for long-lasting durability

• Color-coded emerald green for easy identification

• Compatible with most Tokyo Marui-spec AEG gearboxes

Specifications:

• Material: Hardened spring steel

• Compatibility: Tokyo Marui, EMG, Matrix, and other TM-spec AEGs

• Color Code: Emerald (MS120)

• Velocity: Approx. 400 FPS (0.20g BB)

About Prometheus & Laylax:
Prometheus is a division of Laylax, a leading Japanese manufacturer known for their exceptional airsoft upgrade parts. With over 20 years of engineering excellence, Laylax products are trusted by competitive players, technicians, and serious airsoft enthusiasts around the world. Their focus on precision tolerances and high-grade materials ensures every part performs with reliability and consistency in demanding gameplay scenarios.

Whether you’re building a DMR or simply upgrading your field rifle for improved range and power, the Prometheus MS120 Upgrade Spring offers the performance and reliability you need.