:Re-sleeve worn or seized cylindersAn economical and available solution for riders, racers and engine builders everywhereCentrifugal castings used in these sleeves are made from an alloy of carbon, chrome and molybdenum of 200 Brinell hardness, ensuring ease of installation, trouble-free boring and a dependable, long-lasting engineSPECIAL NOTE: Cylinder Type:AC – Original cylinder bore is alloy chrome-plated, nikasil or electro-fused; cylinder must be bored to accept new sleeveFeel free to email with any questions. Engines with these big bore sleeves create good HP, and great bottom end.