If you are having trouble controlling the temperature of your cooling or heating system for those accuracy demanding projects, this product is what you need. Plug desired appliance into the piggy-back which plugs into a 115V outlet, the controller will turn the appliance ON or OFF when the temperature rises or falls below a setpoint. Less than ±2°F variance in accuracy and -4 to 140°F range. Probe equipped with a 3-1/2 Foot cable. Mounting brackets included. Controls up to15 Amps. UL-rated relay may be used with equipment to 1800Watts. 2 AAA batteries included. NIST Traceable.