... Universal Socket 1. Material: alum. Frame + Steel Strengthen Plate + Silver alloy contact material** Alum. Frame: fire retardant, no electric ... ** Phosphor Bronze: high resilience, antioxidant, good electric conductivity** Brass: good electric conductivity2. Rating: 125V, 4A3. Life Span: ... procedure. There are lifespan test, insulation resistance test, electric strength test, heat test , etc. Qulity is ...