ProX Racing Parts Ultra-Light steel rear sprockets all manufactured from premium quality ?Qste 420 & 460? high strength steel and offer superior durability, even under the most extreme riding circumstances and will last 2-3 times longer than aluminum sprockets made from T7075-T6. Perfect fit together with the drive chains Fits Beta RR 250\300 2 str Beta RR 350-498 2013-2022 The front sprockets are grooved and ultra-light and are the top level quality sprockets Manufactured from low corrosion SCM435 Ni-Chrome Molybdenum steel, featuring a low carbon core to prevent breaking while the case hardened surface offers maximum wear resistance Precision CNC machining ensure a perfect fit and the lightweight design including lightening holes offer ultimate performance The sprockets also come with self-cleaning dirt grooves to extend chain and sprocket life to the max