internal jumpers are available for 0.75-25mm2 terminal blocks, external jumpers are available for 0.75-6mm2 blocks Unique plate internal (external) connection: internal jumpers are available for 0.75-25mm2 terminal blocks, external jumpers are available for 0.75-6mm2 blocks. Unique centre marker system: Marker system can mark terminal blocks quickly and snap in the centre of terminal blocks; Type by computer, clear and obvious. Transparent dust protected cover: Transparent polycarbonate dust protected cover can prevent dust and other matter. Performance characteristic: 1. All the Mechanical property are accordance with IEC60947-7-1 and GB14048.7 Standards, like Mechanical Strength, Installation, Durability for Bending, Durability for Drawing out; 2. All the performance item of insulation house are accordance with GB14048.7 Standards, like Moisture and Thermal Endurance, Thermal Endurance, Fire Hazard Performance, Comparative Tracking Index (CTI); 3. All the performance item for electrical performance are accordance with IEC60947-7-1 and GB14048.7 Standards, like Dielectric Property, Voltage Drop, Temperature Rise and Short-time Withstand Current