The 491820 is a 50-amp, 690 Vac / 700 Vdc, 22mm x 58mm fuse manufactured by DF Electric. It has an “aR” rating, designating a low-resistance design for increased performance. It is designed to protect sensitive equipment from short circuits, overloads, and other electrical threats. The fuse is UL, CSA, and VDE standard-approved, making it suitable for industrial and commercial applications.