LLNRK Series UL Class RK1 Dual Element Time-Delay POWR-PRO fuses provide superior overload and short circuit protection for service entrance, main, feeder and general-purpose branch circuits up to 600 amperes. LLNRK/LLSRK series fuses can be installed in existing Class H fuse blocks to upgrade systems containing lower interrupting rating Class H one-time or renewable fuses. Applications: all general-purpose circuits, motors, transformers, solenoids, fluorescent lighting, all system components with high in-rush currents.