The Rheem-Ruud SP21277 Ignition Control Module is an original equipment manufacturer (OEM) replacement component designed for compatible Rheem and Ruud gas-fired heating equipment, including specified gas water heaters. It manages the electronic ignition sequence by coordinating the gas valve and spark igniter to initiate burner operation. https://www.partshnc.com/rheem-ruud-sp21277-ignition-control-module