LLSRK Series UL Class RK1 Dual Element Time-Delay fuses provide superior overload and short circuit protection for service entrance, main, feeder and general-purpose branch circuits up to 600 amperes. 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.