The Murata PRG21BB150MB1RK is an electronic part that contains a Positive Temperature Coefficient (PTC) Thermistor with a resistance of 15 ohms at 20 volts. A PTC thermistor is a temperature-sensing device commonly used in industrial and automotive applications. This type of device is made of a special ceramic material that has a positive temperature coefficient, meaning the resistance increases as the temperature rises. The PRG21BB150MB1RK is designed to detect and react to temperature changes quickly, making it a useful component in many systems that require reliable and accurate temperature sensing. Additionally, this part is rated to withstand up to 125° Celsius and has a low thermal noise level.