After the plastic-injected case is equipped with contacts and fuse links, the bases are formed by welding or riveting both capable of being multi-phase structured. FB15C, FB16-3J, FB19C-3J, Rt19 are open-structure, and others are semiconcealed structure. There are five fuses sizes available to choose from for the same fuse base of RT18N, RT18B and RT18C, There are two sets of in-out lines for RT18N. One is
installed with fuse links fuse links of the according size. The other is a permanent open contacts with double breaking points. The whole base unit can cut the power. Rt18 bases are all DIN rail installed, among which the RT18L is equipped with safety lock against wrong operation in the breaking state.