Billet Spring Seats – KYB 48 mm Upgrade the OEM plastic spring seat with the Krooztune Billet Spring Seat & Preload Adjustment System, designed for KYB 48 mm motocross forks with 29mm cartridge tubing. CNC machined from high-strength aircraft-grade aluminium, our billet spring seat provides a strong, precise and durable replacement for the OEM plastic component. An integrated spring guide bush is supplied pre-installed for smooth operation, accurate spring location and long service life. Precision 1.5 mm Preload Adjustment The key feature of the Krooztune system is the ability to accurately tune fork spring preload in 1.5 mm increments. While the preload circlip positions are spaced at 3 mm centres, our unique offset billet preload spacers can be rotated 180° to alter their effective installed height by 1.5 mm. This gives suspension tuners significantly finer control over spring preload without relying on additional loose shims or conventional spacer combinations. Fine preload adjustment allows the fork setup to be better matched to rider weight, spring rate, ride height and the desired initial fork feel. Direct OEM Replacement Installation is simple. The Krooztune billet spring seat directly replaces the OEM plastic spring seat while retaining the original OEM spring base, circlip and retention system. No permanent modification to the fork is required. Yamaha KYB Fitment YZ250F: 2019–2026 YZ450F: 2019–2026 YZ250FX: 2020–2026 YZ450FX: 2020–2026 WR250F: 2020–2026 WR450F: 2019–2026 Fits KYB 48 mm front forks , this may include other models with 29mm OD cartridge tubing. Includes standard, special-edition and anniversary models where applicable. Features CNC machined aircraft-grade aluminium construction Replaces the OEM plastic spring seat Integrated spring guide bush supplied pre-installed 1.5 mm spring preload adjustment increments Offset billet preload spacer system Uses the OEM spring base and circlip retention system Allows precise individual preload setting between fork legs Strong, durable and serviceable design Designed specifically for professional suspension setup Developed and manufactured by Krooztune Suspension Kit Includes 2 × Krooztune Billet Spring Seats with guide bushes installed Billet preload circlip spacer set Installation instructions Applications: KYB 48 mm motocross forks - current generation with 29mm cartridge tubes Krooztune Performance Hard Parts — designed to give suspension tuners greater control over the details that make a great setup.