A fuse found in amperage sizes greater than 60amp. If you are asked for a knife blade safety switch, it refers to a 100amp or greater switch because the 60amp will be a cartridge style fuse. Safety switches come in 30a, 60a, and then jump to 100a although knife fuses are available starting at 70a, 80a, etc. The item code shown below is a reference to one type of fuse and isn't an indication at all of what the customer wants. You need to know amperage, voltage, UL Class, interrupting rating and most importantly, application.