NO.663-R is a Class R fuse reducer designed for Bussmann series FRS-R/LPS-RK 600 V fuses, enabling the installation of fuses up to 30 A into 60 A fuse blocks or disconnect switches. The reducer maintains strong contact both mechanically and electrically, ensuring reliable performance in electrical distribution systems. It is rated for 600 V operation and is UL Listed (Guide IZZR, File E12853) and CSA Certified (Class 6225-01, File 47235), with RoHS compliance. The reducer fits into most panels and switches including dead-front types, making it suitable for retrofit applications where smaller fuses are required without replacing the existing fuse block infrastructure.