Applicable: The 77707-0010 Thermal Regulator Kit Replacement for Pool to use with for Master Temp, for Sta- Max-E- pool and spa heaters. Product kit includes regulator, spring, clip and cap. Part Number 77707-0010 How to Test: The 77707-0010 Thermal Regulator Kit Compatible with for Mastertemp SR400 parts, SR333NA, SR300, SR200NA, SR200 and 125 Low Nox Pool Heater Reliable: The 38000-0007S Thermal Regulator for Pool and Spa Heater has undergone extensive testing that ensures your swimming pool heater running well, such as heater showing E-05 error fixing; quickly warm the water up and reach the comfortable temperature you want Easy Installation: The 77707-0010 Thermal Regulator Kit as an assist part, easy to install, located between the inlet and outlet water connections on the water manifold, completely fit, no special adjustment Please note: the physical slightly color difference or difference, does not affect the use, please do not mind, thank you! Colour:Photo Color Material:Metal Package Contents: 5 x Heater Temp Regulator Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.