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.It has a cylinder bore of 54 mm and measures 87 mm x 80 mm x 54 mm overall, with an inner diameter of 84 mm and height of 16 mm.The cylinder block is constructed from aluminum with ceramic material integrated into the inner wall to support wear resistance.It weighs 1650 grams and is silver in color.One cylinder block is included per package.Installation instructions are not provided.This replacement part is manufactured independently.All brand references are used solely to denote compatibility with listed models.