The Bussmann NO.263-R is a Class R fuse reducer designed to allow the use of smaller fuses in larger fuse blocks or switches. Specifically, it enables a 30-amp fuse to be installed in a 60-amp fuse block, maintaining proper electrical protection without the need to replace the entire block2. This non-indicating accessory is rated for up to 60 amps and 250 volts, and comes in packs of 10 pairs. It's especially useful in electrical panels and assemblies where space and compatibility are critical, and it fits most panel types including dead front styles2.