ATO, Autofuse blade fuse was patented and introduced in 1976 by Littelfuse. It became the international fuse standards by 1981. It is currently found on most trucks, cars, buses and off the road vehicles world-wide. Littelfuse designed industry standard color coding to indicate amp rating. Aftermarket - 257 Series - carded 25 piece PRO-TEK professional pack of ATO fast-acting automotive blade fuses.