The BK/GDC-4A is a 5 mm × 20 mm time-delay glass tube fuse designed for circuit protection in industrial and commercial applications. It features a nickel-plated brass endcap construction and is rated at 4A nominal current with a 250V voltage rating and 40A interrupting capacity at 50 Hz. The fuse exhibits a typical DC cold resistance of 0.0139 O and a typical melting current of 71.8A, with a voltage drop of 67 mV/µ measured at 20°C ambient temperature at rated current. It is designed to IEC 60127-2 standards and provides reliable time-delay protection with low breaking capacity, making it suitable for equipment requiring coordinated overcurrent protection and reduced nuisance tripping.