To fit the previous style brake disc.
All used parts are graded based on condition to give you a better idea of what you are purchasing and helps you compare from part to part. Grading is as follows;
Grade 1 - Very good condition. Item like new with minimal signs of use.
Grade 2 - Good used condition. Item will have signs of use but no heavy wear.
Grade 3 - Acceptable used condition. Item will have heavier signs of use but is still in a usable state.
Grade 4 - Item has heavy signs of use and wear. May require repair or adjustment.