ProTaper's revolutionary SELA Device (Self-Engaged Launch Assist) solves a problem faced by all motocross racers, no matter their skill level: setting a start device alone is awkward at best and impossible at worst. With its patent-pending self-engaged twist dial, SELA can be easily set without any assistance, giving riders the freedom to practice starts and line up for races by themselves. During a start, SELA makes it possible to temporarily compress the motorcycle's front suspension, reducing its tendency to wheelie under acceleration. This optimizes rear wheel traction, allowing the rider to be more aggressive with the throttle and launch down the start straight with greater control. Easy to use: twist the dial, ride the bike and grab the front brake to compress the fork, this will let the device pass by the dial enough for the device to engage. On the first hard brake or jump the systems dis-engages and your back to normal. Forged aluminum alloy construction optimizes weight savings, strength and durability. A dual-hinged receiver ring makes for quick and convenient installation without removing the front wheel or fork. Hard-anodized moving parts maximize resistance to corrosion and wear. Durable laster-etched graphics, including engagement confirmation markings. Adjustable for different suspension sizes from 2.13" - 2.25" - Came off of a CRf450 2021. Check fitment before purchasing: https://www.rockymountainatvmc.com/parts/protaper-sela-device-p