RRGS/JISO DIO 54.5mm air cooled cylinder. 
 
Product Description
Manufacture: RRGS/JISO
Fit Models:
(1)HONDA DIO AF18 AF25 ARNADA (F5A F5B)
(2)HONDA SUPER DIO AF27 AF28 DIO ZX (F5Q F5P) 
(3)HONDA ELITE S / SE / SR AF16 1994-2001
(4) SYM DD
Size:
(1)Outside Diameter:59mm
(2)Cylinder Height:81mm
(3) skirt:23mm