This is a replacement cylinder block for 2-stroke motorcycle engines.It is compatible with YZ125 models from 2005 to 2021 and YZ125X models from 2020 to 2022.The part number is 1C3-11311-21-00.The cylinder bore measures 54 mm.The construction combines aluminum and ceramic materials on the inner wall.Dimensions are 87 mm x 80 mm x 54 mm and 84 mm x 16 mm.The weight is 1650 g.The color is silver.Includes one cylinder block per package.Fits YZ125 and YZ125X as specified. ote: This is a third-party compatible part.Brand/model citations do not imply sponsorship or approval.