FLSR350 - Littelfuse FLSR Class-RK 5 Fuse The FLSR Series - Class RK5 Family Littelfuse FLSR series fuses have been the superior UL Class RK5 dual-element time-delay fuses, and are the most widely used class of fuses. FLSR series fuses provide excellent protection for all types of circuits especially those containing motors. However, users and specifiers should consider the significant benefits offered by Indicator fuses. Applications: Service entrance switches Switchboard main and feeder switches Motor control center mains and motor branch circuits Individual fused combination motor controllers Distribution panelboards Industrial control panels Protection of fully-rated panelboards and loadcenters All general purpose circuits Safety: 200, 000 A.I.R.- Reliable interruption of all overcurrents up to 200, 000