Littelfuse 451 Series NANO2 Surface Mount FusesLittelfuse 451 series of NANO2 surface mount fuses are very small wire-in-air (WIA) square shape surface mount devices which are suitable for a variety of secondary side circuit over-current protection applications.Very fast actingSmall sizeLow temperature de-ratingApprovalsCSA, ULApprovalsUL, CSASurface Mount TechnologySurface mount fuses offer considerable space (and time) saving features for low voltage applications. The FF types are ideal for protection of high value silicon IC's e.g. alarm systems, audio/visual equipment, computer boards, portable telephones, power supplies, medical apparatus etc.