4” Because

Prevents problems from occurring when motorbikes

Power cable ended in bare wires and fused

com/assets/155510P

so it perfectly adapts to the bodys anatomy

BMC Air Filters - Honda SH300i High Performance Air Filter Option:Standard (FM636/04) 4” BecauseThis High Performance air filter is made from premium material that allow increased air flow and filtration efficiency, blocking containment as small as 7 microns (compared with 10 microns in most other filters). BMC air filters are produced using a "Full Moulding" system. This prolongs the life and durability of the filter. The rubber used in BMC air filtering systems has a long life with optimum adhesion characteristics to all shapes of airboxes.