2-wire potential relay and start capacitor. 3.5-5.0 ton maximum torque hard start device. Hard start devices extend the life of compressors considerably by bringing them up to full speed more quickly and efficiently. They also assist compressors in starting under very adverse ambient conditions such as low voltage or high head pressures.2-wire design for easy installationExtend the life of compressorsOEM tested and approved3.5-5 ton units