Fastrax 23T Black Aluminium Double Servo Horn KO Sanwa FAST315B

Overview

The Fastrax 23T Black Aluminium Double Servo Horn (KO/Sanwa) is a premium upgrade component designed for serious RC enthusiasts who demand durability and precision in their steering and throttle assemblies. Whether you're running a high-performance RC buggy, crawler, or truck, this heavy-duty servo arm represents a significant step up from standard plastic alternatives. Built from machined aluminium and finished in professional black anodising, this servo horn is engineered to withstand the demanding conditions of off-road RC racing and bashing, making it an essential upgrade for anyone looking to improve their RC car UK setup.

If you're experiencing servo arm flex or breakage during aggressive steering inputs or throttle control, this component solves those problems with robust engineering and intelligent design. The Fastrax servo horn is compatible with both KO and Sanwa servo systems, meaning you can retrofit it to many popular RC vehicles without needing to replace your existing servos. This compatibility makes it an economical choice for upgrading your RC equipment, allowing you to boost performance without a complete servo swap. Available in multiple spline sizes for different servo types, this is the go-to upgrade for bashers and racers across the UK who take their RC hobby seriously.

RC Model Shop stocks this essential upgrade to help you build a more reliable and responsive RC vehicle. Whether you're preparing for competition or simply want to eliminate servo arm failure during weekend bashing sessions, this Fastrax servo horn delivers the strength and precision you need.

Key Features

• Black Anodised Machined Aluminium Construction — The servo horn is machined from high-grade aluminium and finished with professional black anodising, providing excellent strength-to-weight ratio whilst maintaining a polished, competition-grade appearance. This material choice ensures the servo arm resists flex and bending during aggressive steering inputs, which is critical for maintaining steering precision in RC cars and trucks.
• Double Servo Arm Configuration — The double arm design provides superior control authority and leverage, allowing your servo to command larger steering angles with smoother, more predictable response. This is particularly valuable in RC crawlers and off-road vehicles where steering finesse directly impacts performance.
• 23T Spline Size — This servo horn features a 23-tooth spline that matches the industry-standard KO and Sanwa servo output shafts. The 23T size is one of the most common fitments across RC vehicles, making this an extremely versatile upgrade component.
• KO and Sanwa Compatibility — Engineered to fit both KO and Sanwa servo brands without modification, this universal compatibility means you can use this upgrade across multiple RC vehicles in your collection, maximising value and reducing the need to stock different horn sizes.
• Additional Screw Clamping System — Beyond the standard spline fit, this servo horn features supplementary screw clamping for extra strength and security. This additional fastening mechanism prevents slippage and ensures the servo arm remains absolutely locked in position under extreme steering loads, essential for reliable RC performance.
• Includes Mounting Hardware — Each servo horn comes with a mounting screw and an aluminium countersunk washer, ensuring you have everything needed to install it immediately on your RC vehicle. The countersunk washer distributes clamping force evenly across the servo spline, reducing stress concentration and improving durability.
• Fixed Mounting Design — This is a fixed servo saver configuration, meaning the arm does not rotate freely. This design provides direct, responsive steering control with zero backlash, which is ideal for racing applications and precision RC driving where immediate steering response is critical.

Technical Performance

This Fastrax servo horn represents a significant engineering upgrade over standard plastic servo arms commonly found on entry-level RC equipment. The machined aluminium construction provides substantially greater rigidity than injection-moulded plastic, directly translating to improved steering precision and control in your RC buggy, truck, or crawler. The black anodised finish is not merely cosmetic; anodising creates a hard oxide layer on the aluminium surface that provides superior wear resistance, corrosion protection, and durability. This is particularly important if you're using your RC vehicle in varying UK weather conditions or wet terrain. The 23T spline configuration is the industry standard for mid-sized servo systems, making this horn compatible with the majority of KO and Sanwa servos found in popular RC vehicles across the UK. The double arm design maximises mechanical advantage, allowing your servo to deliver strong, responsive steering control without requiring increased servo torque, which would otherwise drain your battery faster and potentially overheat your servo during extended running sessions. The additional screw clamping system is engineered to prevent the servo horn from slipping on the servo spline under sustained load—a common failure mode with plastic servo arms that can lead to unresponsive steering at critical moments. The aluminium countersunk washer distributes the clamping force evenly, reducing localised stress on the servo spline and extending the working life of both the servo horn and the servo itself. This is precision RC engineering at an accessible price point, delivering the reliability you need whether you're competing in RC racing events or enjoying recreational bashing sessions with friends.

What's in the Box

• Fastrax 23T Black Aluminium Double Servo Horn
• Mounting screw
• Aluminium countersunk washer

Frequently Asked Questions

• Which RC servos does this servo horn fit? — This servo horn is engineered to fit KO and Sanwa servo systems with a 23-tooth spline. These are industry-standard servo brands used in countless RC buggies, trucks, crawlers, and on-road vehicles across the UK. If your RC vehicle uses a KO or Sanwa servo, this horn will fit without modification.
• Why would I upgrade from a plastic servo arm to aluminium? — Plastic servo arms flex and bend under load, reducing steering precision and potentially breaking under aggressive use or high servo torque. This machined aluminium servo horn provides approximately 8-10 times the rigidity of plastic, delivering immediate steering response and lasting durability through thousands of running hours. If you've experienced servo arm breakage or noticed spongy steering in your RC car, this upgrade directly addresses those issues.
• What does the additional screw clamping system do? — The extra screw clamping provides backup security beyond the spline fit alone. Under extreme steering loads, plastic servo arms can slip on the spline, causing your steering to become unresponsive at critical moments. The supplementary clamping bolt locks the horn firmly to the servo shaft, preventing any movement and ensuring consistent steering feel throughout your running session.
• Is this suitable for beginners? — Whilst beginners can certainly use this upgrade, it's more valuable for intermediate and advanced RC drivers who have experienced servo arm failure or who demand precision control in racing or challenging terrain. Beginners can certainly install it themselves as an upgrade to their existing RC vehicle, and the included hardware makes installation straightforward.
• What is the difference between fixed and servo saver servo horns? — This is a fixed servo horn, meaning it does not rotate freely on the servo shaft. Fixed designs provide direct control with zero backlash, ideal for racing and precision driving. Servo saver designs (sold separately) allow the horn to rotate slightly, providing impact protection for the servo and servo gears during crashes, making them better suited to aggressive bashing. Choose fixed for racing, servo saver for bashing.
• How do I install this on my RC vehicle? — Simply remove your existing plastic servo horn by unbolting it from the servo spline. Slide this aluminium horn onto the same spline, align it to your preferred steering angle, insert the mounting screw through the countersunk washer, and tighten firmly. The fixed design means there's no rotation needed—just secure it in your desired position and you're ready to drive.
• Will this improve my RC car's steering response? — Yes. By eliminating flex in the servo arm, you'll immediately notice sharper, more responsive steering with better feedback. This is particularly noticeable in RC buggies and crawlers where steering precision directly impacts lap times and obstacle navigation ability.

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 23T BLACK ALUMINIUM DOUBLE SERVO HORN (KO/SANWA) FAST315B 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.