COMPATIBLE HEATER MODELS: This O-ring kit is designed for use with Pentair MasterTemp and Sta-Rite Max-E-Therm pool and spa heaters. Compatible with the following models: MasterTemp: 200, 250, 300, 333, 400 series; including model numbers 460792, 460793, 460730, 460731, 460732, 460733, 460734, 460735, 460736, 460737, 460805, 460806 Max-E-Therm: SR200NA, SR200HD, SR200LP, SR333NA, SR333HD, SR333LP, SR400NA, SR400HD, SR400LP REPLACEMENT PART NUMBER: This kit directly replaces OEM part number 77707-0120. It includes the manifold O-rings required for sealing the tube sheet and heat exchanger coil connections. MATERIAL SPECIFICATION: Manufactured from EPDM rubber. This material is selected for its resistance to elevated temperatures, water exposure, and common pool and spa chemicals, ensuring compatibility with the operating environment of pool heater systems. FUNCTIONAL APPLICATION: The O-rings in this kit are designed to seal the connection points between the heater manifold, tube sheet, and heat exchanger coil. Replacement is indicated when the existing seals exhibit hardening, cracking, loss of elasticity, or when visible leakage is present at the manifold connection. INSTALLATION: Installation requires removal of the manifold assembly, opening the cover, and replacing the existing O-rings with the new seals. The kit is suitable for service by pool maintenance professionals, technicians, and qualified DIY users. No specialized tools are required.