The Toyotomi 4″ Chimney Install Adapter Kit is an accessory designed to enable proper chimney venting for compatible Toyotomi oil-fired water and hydronic heaters, including models such as the OM-122DW and OM-128HH. It provides a secure transition between the heater’s flue outlet and a 4-inch chimney connection, ensuring a safe exhaust path for combustion gases and supporting efficient vent performance. This installer-ready adapter kit helps simplify vent installation and maintain compliance with manufacturer venting requirements for outdoor chimney applications.