If you ride a...
Cruiser board you'll need Film 4.25" (105mm)
7-7.8" board you'll need Film 5" (125mm)
7.8-8.2" board you'll need Film 5.25" (135mm)
8-8.3" board you'll need Film 5.5" (145mm)
8.3" board or bigger you'll need Film 6" (155mm)