Custom developed by BBR Motorsports for mini four-strokes. Increased spring rate for fast / aggressive adult mini riders. This is the most important upgrade you can make for an adult sized rider for improved suspension action. The stock suspension is too soft for most adults. Increased spring rate for adults. Preset and stress relieved for long life. Custom wound from aircraft-quality spring steel. Powder coated finish. Note: Fits stock rear shocks on CRF50 / DRZ70 models.