This is the replacement drive washer for the FS-120 OS engine. PACKAGE INCLUDES: 1- Drive washer (aluminum) 1- Woodruff key SPECS: Diameter face: (34mm) Engine side diameter: (31mm) Inside diameter: (12mm) Width: (14mm) approximately 5/8″ sek/3-31-94 BOX DIMENSIONS: 2.13″ W. X .63″ H. X 3.50″ L. BOX WEIGHT: .06 LBS.