System Sensor 52051 Low Profile Addressable Heat Sensor System SensorLow profile System Sensor addressable heat detector.58°C fixed temperature and rate of rise (Class A1R), 58°C fixed (Class A1S) and 78°C fixed (Class BS) available. Heat Class Choose an optionA1R Rate of RiseA1S - 58°C FixedBS - 78°C Fixed Quantity Add to basket Clear options