Honda dio af18 af27 af28 af34 drive belt 641 x 15.5 x 30
 
Fits:
 Dio Live (AF34), Dio J (AF34), SR (AF35)
Dio Cesta(all ), Dio ST 'Super' Dio SR (AF28)
'Super' Dio (AF27) (all) , Dio SP (AF25) (all) 
all Impax S, DJ-1 DJ-1L DJ-R (chassis number AF12-1309466 and higher)
Super Tact (AF09) Tact / Stand Up / S (AF16,24, AF30,31) Tact (AF51)
all Giorno (AF24), all Julio (AF52)
all Dio Fit (AF18)
 
Will fit some other models too. A quick google search should tell you whether it will fit your model. 
 
Same as these honda part numbers: 23100-GG2-750, 23100-GR1-315, 23100-GZ5-003, 23100-GZ5-013, 23100-GR7-003, 23100-GN2-003
 
Other belt sizes available;
Groove Angle: 30° 
15.5 - 650 
15.5 - 642 (interchangeable with 650) 
15.7 - 666 
16.6 - 792 
17 - 790 
17.5 - 710
17.5 - 765
17.5 - 845
17.7 - 729 
18 - 654
18 - 664
18 - 669 
18.5 - 675 
19 - 650 
20 - 815 
20 - 743 
20 - 842 
20 - 835 
 
Decent quality, we install these at JRMotorcycles workshop and highly recommend them.
Installation available in Rolleston, Christchurch.