WHY BORE YOUR OLD CYLINDER?????????? USE IT FOR A FISHING WEIGHT, OR A PIN/PENCIL HOLDER. WITH THIS KIT YOU WILL GET EVERYTHING IN THE PICTURE. CYLINDER - HONED AND READY TO GO-, PISTON,PISTON RINGS,PISTON PIN, PISTON PIN CLIPS AND A TOP END GASKET SET. JUST BOLT-ON AND GO. THIS KIT IS TO BE USED ON ANY Z50A OR R THRU "81" ENGINES. THIS SHOULD BE USED WITH THE STOCK 50CC HEAD. THE CYLINDER SAYS 49CC ON THE CASTING. (1P39FMB-100007)/1-76/311W @ e NEW HIGH QUALITY STANDARD PISTON KIT ALL_Z50A'S 06131-036-020 1/22T (100076) (S1407)THESE WILL FIT 69 THRU 78 Z50A'S YOU GET THE PISTON, PISTON RING SET, PISTON PIN AND PISTON PIN CLIPS WITH THIS KIT. WILL ALSO WORK IN 1979 TO 1981 Z50R'S 100076 (S1407)