The GE Q-Line 30 Amp 1/2 in. Single-Pole Circuit Breaker has a case made of heat-resistant thermoset for stability and structural integrity. The unit has a tin-plated copper stab to create a reliable, permanent and corrosion-resistant connection. The circuit breaker has a dedicated calibration screw which is cemented to prevent shifting. The attached screw creates a stable calibration for optimum performance.