Hi this ATAC spacer is made to fit Honda cr125 from years 87-89.The spacer enhances the volume of the ATAC exhaust chamber and gives you more low-end power . It was used by many pro-riders back in the day. Simple installation, just fits between the chamber manifold and the chamber it self. All you need is some longer bolts. Made from 6082 billet alloy. Please check out my other evo mx parts. Thanks