Fastrax 15T Jumbo Black Aluminium 3-in-1 Servo Horn for Savox Multiplex Losi Hitec FAST321B

Overview

The Fastrax 15T Jumbo Black Aluminium 3-in-1 Servo Horn (FAST321B) is an essential upgrade for RC car enthusiasts in the UK looking to enhance their servo performance and reliability. This premium aluminium servo arm is specifically engineered for large-scale RC applications and offers unparalleled versatility with its innovative three-way design. Whether you're running a competitive RC buggy, a rock crawler, or a general-purpose RC car, this servo horn provides the flexibility and durability you need for consistent performance across multiple servo types and mounting configurations.

Designed by Fastrax, a renowned manufacturer of quality RC components and accessories, this servo horn represents a significant advancement in servo arm technology. It's compatible with an impressive range of popular servo brands and models, including Savox Jumbo servos, Multiplex Rhino Digi 4 servos, Losi 5T servos, and Hitec servos, making it an incredibly practical choice for modellers with diverse RC fleets. The 15-tooth spline ensures compatibility with large-scale servo applications, whilst the black aluminium construction provides both lightweight performance and exceptional durability that serious RC car UK enthusiasts demand.

What truly sets this servo horn apart is its ingenious three-way fit design, allowing you to choose between left or right 90-degree L-shaped configurations or a straight double arm setup simply by rotating the top and bottom arms to your desired shape and direction. This level of customisation means you can adapt a single servo horn to multiple applications, saving money and reducing parts clutter in your RC workshop.

Key Features

• 3-in-1 Multi-Configuration Design — This servo horn offers unprecedented flexibility with the ability to function as a left 90-degree arm, right 90-degree arm, or straight double arm configuration, simply by rotating the top and bottom arms to match your specific steering or throttle linkage requirements, eliminating the need to purchase multiple different servo arms for different applications.
• Premium Aluminium Construction — The servo horn is machined from high-quality black aluminium, providing an excellent strength-to-weight ratio that improves handling characteristics whilst maintaining durability through thousands of steering inputs and servo cycles without fatigue or failure.
• Machined Lugs with Secure Locking System — The precision-engineered lugs help secure the arms into place for a solid, rock-solid fit that won't shift during aggressive driving or racing, ensuring consistent steering geometry and eliminating the frustration of arm movement that can compromise control feel and directional accuracy.
• Ultra-Tight Side Clamp Design — Once mounted to your servo, the specially designed side clamp mechanism provides an ultra-tight grip on the servo gear splines, virtually eliminating any risk of slippage, stripping, or the arm becoming dislodged during high-demand driving situations where other servo horns might fail.
• 15-Tooth Spline Compatibility — The 15-tooth spline design is specifically engineered for large-scale servo applications, providing secure engagement with Savox Jumbo, Multiplex Rhino Digi 4, Losi 5T, and Hitec servo platforms that demand robust, reliable connections.
• Single Arm Washer Included — Should you only need a single arm application rather than the full double-arm configuration, a specially designed washer allows you to use just one arm, further increasing the versatility and value proposition of this component.
• Servo Saver or Fixed Mount Options — This servo horn is compatible with both servo saver and fixed mounting applications, giving you complete freedom to choose how you want to configure your RC car's servo linkage depending on your driving style, terrain, and performance requirements.
• Versatile Multi-Brand Compatibility — Unlike many servo horns that only work with specific servo brands, this Fastrax design accommodates Savox, Multiplex, Losi, and Hitec servos, making it an exceptionally practical choice if you're building or maintaining multiple RC cars with different servo brands.

Technical Performance

The Fastrax 15T Jumbo Black Aluminium 3-in-1 Servo Horn represents engineering excellence in RC component design. Precision-machined from premium-grade black aluminium, this servo arm delivers exceptional rigidity and durability essential for demanding RC applications. The 15-tooth spline specification ensures compatibility with large-scale servo platforms that require robust, reliable engagement without slip or movement. The side clamp design exerts tremendous pressure on the servo spline, effectively locking the arm in position and preventing the common problem of arm rotation during aggressive steering corrections or high-load situations. The machined lugs provide positive positioning reference points, ensuring arms maintain their orientation and relationship to each other regardless of driving conditions or servo load cycling. The inclusion of a specialist washer for single-arm applications demonstrates Fastrax's attention to real-world usability—many RC car UK builders find they need alternative configurations as their projects evolve. Whether you're installing this on a Savox Jumbo servo commonly found in large-scale buggies, a Multiplex Rhino Digi 4 used in crawler platforms, a Losi 5T servo in competition trucks, or a Hitec servo in various applications, the engineered fit ensures consistent performance and eliminates the binding, stripping, and slippage issues that plague lower-quality servo arms.

What's in the Box

• 1x Fastrax 15T Jumbo Black Aluminium 3-in-1 Servo Horn (FAST321B)
• Specialist washer for single-arm configuration option

Frequently Asked Questions

• Which servo brands does this 15T servo horn work with? — The Fastrax 15T Jumbo servo horn is specifically designed to fit Savox Jumbo servos, Multiplex Rhino Digi 4 servos, Losi 5T servos, and Hitec servos, making it an excellent universal choice for modellers running diverse servo platforms across their RC car fleet. The 15-tooth spline specification ensures secure, reliable engagement with these large-scale servo gear systems.
• What does the 3-in-1 configuration system mean in practical terms? — The 3-in-1 design refers to the servo horn's ability to function in three distinct ways: as a left 90-degree L-shaped steering arm, as a right 90-degree L-shaped steering arm (simply by flipping the orientation), or as a straight double-arm configuration for throttle linkage or alternative steering setups. By rotating the top and bottom arms to your desired angle and direction, you can adapt this single servo horn to multiple applications without purchasing different arms for each configuration.
• Is this servo horn suitable for beginners in RC car UK racing? — Absolutely—this servo horn is an excellent choice for beginners because its robust construction means it's highly resistant to damage from inevitable mistakes during learning, its universal compatibility with multiple servo brands means it's likely to work with whatever servos your RC car came with, and its three-way design means you have flexibility as you experiment with different linkage geometries and mounting positions as you develop your skills.
• What is the advantage of the side clamp design compared to standard servo arms? — The side clamp mechanism provides significantly superior holding force compared to traditional horn designs, creating an ultra-tight grip on the servo gear splines that virtually eliminates slippage, gear stripping, and the arm becoming dislodged during aggressive steering inputs or high-load situations—critical advantages for competitive driving or rough terrain RC car UK applications.
• Can I use just one arm if my application only requires single-arm configuration? — Yes—Fastrax includes a specially designed washer that allows you to use just one arm if your steering or throttle linkage only requires a single connection point, improving aesthetics and reducing weight whilst maintaining the servo horn's security and rigidity.
• How does the machined lug system improve performance? — The machined lugs provide precision contact points that position and secure the arms, preventing rotation or shifting during servo operation, ensuring your steering geometry remains consistent lap after lap or run after run without gradual deterioration that lower-quality servo arms often experience.
• Is this servo horn compatible with servo saver applications? — Yes—this servo horn is explicitly designed to work with both servo saver and fixed mounting applications, giving you complete flexibility to choose whether you want the shock-absorbing protection of a servo saver (ideal for bashing) or the direct, responsive feel of fixed mounting (preferred for racing).

Why Buy from RC Model Shop?

RC Model Shop is a trusted UK RC retailer and authorised dealer for all the brands we stock, including Traxxas, ARRMA, Losi, FTX, Hobbywing, Spektrum and more. Based in Walsall, we have a physical store where customers are welcome to come in, view products and purchase in store. Whether you are a seasoned competitor, a weekend basher, or just discovering the world of RC for the first time, our team of experienced RC enthusiasts is here to help you find the perfect setup and provide ongoing support. Order the FASTRAX 15T JUMBO BLACK ALUM 3-IN-1 SERVO HORN (SAV/MUL/HI) FAST321B today with confidence, knowing you are buying from an authorised retailer with genuine products, expert knowledge and a commitment to customer satisfaction. Shop online or visit us in Walsall — we look forward to helping you get the most out of your RC experience.