Compatible with: Yamaha YZ250 1988-1992 Yamaha YZ250W 1989-1990 Yamaha WR250Z 1991-1993 Key differences between cork-based clutch friction plates (black ones) and fiber plates (yellow ones) : Material Composition: Cork-based plates are made from a combination of cork and rubber, while fiber plates are typically made from paper, Kevlar, or other composite materials. Friction Coefficient: Cork-based plates generally have a lower friction coefficient than fiber plates, which can result in a smoother and more gradual engagement of the clutch. Wear and Tear: Cork-based plates are generally softer and more flexible than fiber plates, which means that they can be less prone to causing excessive wear and tear on the clutch system. Fiber plates are more durable and can withstand higher temperatures, but they can be more prone to causing wear on the other components of the clutch system. Heat Dissipation: Cork is a better thermal insulator than fiber, which means that cork-based plates can help to dissipate heat more effectively than fiber plates. This can result in a cooler-running clutch system and reduced risk of overheating and damage to components. Price: Cork-based plates are generally less expensive than fiber plates, which can make them a more cost-effective option for riders who are looking to replace their clutch plates.