This Lochinvar Liquid Propane (LP) Burner Assembly is designed with a #51 orifice. The assembly is engineered to provide efficient and reliable combustion for Lochinvar water heaters and boilers. It's constructed from high-quality materials to ensure durability and longevity. The #51 orifice size indicates the diameter of the hole in the burner, which controls the amount of gas that can flow through it. This specific assembly is intended for use with liquid propane fuel, as indicated by its LP designation. The product ensures optimal performance and safety when installed correctly in compatible Lochinvar appliances.