Bussmann CVR-J-60100-M Fuse Block Cover. Bussmann Fuse Block Cover, Series: JM60100, 100 A, 600 VAC, For Use With: Class J Power Distribution Fuse Block, 6 in Length, 2 in Width, 2 in Height, Thermoplastic. Additional Description: BUSS-CVR-J-60100-M CLASS J 600V 100A FUSE COVER ASSEMBLY. Catalog Description: Eaton Bussmann series CVR fuse block cover, Modular fuse block cover, 100 A, Class J, Non-indicating, 600 V.