0154003.DR 3A FF Surface Mount Fuse, 125V ac/dc. Littelfuse 154 series OMNI-BLOK fuse and holder combinations offer a convenient solution for efficient installation and easy replacement of miniature Littelfuse NANO² surface mount fuses. The 154 series fuse and holder combination can be installed on a PC board in a single, quick, efficient step and further fuse replacement can be accomplished without exposing the PC board to the detrimental effects of solder heat. Littelfuse 154 series OMNI-BLOK’s are suitable for a wide variety of applications.