#3

Used on string trimmers
and small 2-cycle engines

#3.5

Used on string trimmers
and small 2-cycle engines

#4

Used on chainsaws
and larger 2-Cycle engines

#4.5

Used on string trimmers and small 2-cycle engines and some 4 cycle mowers

#5

Used on 4-Cycle Push Mowers,
5.5 to 6.5 Hp Engines

#5.5

Used on 4-Cycle Push Mowers, lawn vacs, snowblowers & blowers.

#6

Used on large 4-Cycle engines, power washers

#8

Used on large 4-Cycle engines,
Commercial mowers, generators