A micro fuse is a radial leaded subminiature fuse, offered in either a cylindrical or rectangular form factor. Micro fuses were originally designed for the U.S. Space Program. The micro fuse is made with either glass, plastic or metal bodies. They are designed to be electrically equivalent to miniature glass cartridge, fuses in a smaller package with higher tolerance to impact and vibration. Micro fuses can plug, into a PC board mounted fuse holder. Micro fuse voltage, ratings typically range from 65 volts AC to 300 volts AC. Micro fuses with voltage ratings up to 450 volts DC are also available. Micro fuses are offered in fast-acting or time lag, versions.