600V CLASS R BLOCK 100A 3 POLE. The new Littelfuse Class H and R blocks offer many advantages over previous generations that are noted in the features and benefits section. Class H and Class R fuse blocks are dimensionally the same, but Class R blocks incorporate a rejection feature, which only allows Class R fuses to be inserted. Features & Benefits: Indication offered on most 250V and 600V versions. DIN Rail releasable for all non-knife blade style fuses. Only one hand is required to release from DIN Rail (lock open lock closed). Universal mounting holes make for easy replacement. Clip designs maximize electrical contact and minimize heat rise. Reinforcing clips are standard on all Class R fuse blocks.