Society of Fuse Engineers
North-American built automobiles up to 1981 had electrical systems protected by cylindrical glass cartridge fuses rated 32 volts DC and current ratings from 4 amperes to 30 amperes. These are known as "SFE" fuses, as they were designed by the Society of Fuse Engineers to prevent the insertion of a grossly inadequate or unsafe fuse into the vehicle's fuse panel.[3][4] These SFE fuses all have a ?1/4 inch diameter, and the length varies according to the rating of the fuse.
A 4 amp SFE 4 fuse is ?5/8 inch long (the same dimension as an AGA fuse of any rating), a 6 amp SFE 6 fuse is ?3/4 inch long, a 7.5 amp SFE 7.5 fuse is ?7/8 inch long (same as an AGW fuse of any rating), a 9 amp SFE 9 fuse is ?7/8 inch long (same as an AGW fuse of any rating), a 14 amp SFE 14 fuse is 1?1/16 inch long, a 20 amp SFE 20 fuse is 1?1/4 inch long (same as an AGC fuse of any rating), and a 30 amp SFE 30 fuse is 1?7/16 inches long.[3]