The 4kW Caldera Low Flow Trombone Heater is a high-performance replacement heater designed for Caldera and Watkins hot tubs with lower water circulation. Its trombone-style design allows for efficient water heating, even in spas that experience reduced flow, making it ideal for models like the Caldera Utopia and Paradise Series. The flow switch and hi-limit sensor enhance safety by ensuring the heater operates within optimal conditions. Additionally, it features a 4kW at 240V heating element and comes with 3/4" hose barb connections for a secure plumbing setup and a 40" pigtail cord for flexible installation.