A10BG0 is Cutler-Hammer A1 Series NEMA Size 0 open-frame 3-pole AC magnetic contactor for three-phase motor control; A10B-1 is its matching factory original main contact replacement kit. Designed per NEMA & UL508 standard for compressor, pump, fan and general machine motor switching, widely used in HVAC & industrial control cabinets, compatible to add external NEMA standard thermal overload relay for motor overload protection.