Mersen Protistor? 10x38 Type gR Fuses. From Mersen, a range of cylindrical ultra-rapid fuses available in a wide range of current ratings to suit most applications. These 10 x 38 Protistor? fuses are designed for the protection of inverters, UPS, variable speed drives and similar discrete semiconductor devices. Features and Benefits. gR class according to VDE 636-23 and IEC 60269-4 Fast acting Current limiting 10 x 38 mm universal size Excellent cycling capability. Applications. UPS Small inverters Motor drives