The BK/MDL-4-R is a 4-ampere time-delay glass tube fuse manufactured by Bussmann, featuring a 1/4" × 1 1/4" (6.4 × 31.7 mm) physical size with nickel-plated brass endcaps and UL Listed construction meeting standard 248-14. It is rated for 250V AC with a 100A AC interrupting rating and exhibits a typical DC cold resistance of 10,000 O, a melting I²t of 67.5 A²sec, and a voltage drop of 0.345V at rated current. The fuse is designed for time-delay operation, providing protection against temporary overcurrents while withstanding normal inrush conditions. It is commonly used in industrial control circuits, power distribution systems, and equipment requiring reliable overcurrent protection with delayed response characteristics.