This Lochinvar burner assembly, identified by the model number NAT 18", is a key component in various heating systems. The assembly includes a #3.0 orifice (ORF), which is responsible for controlling the flow of fuel into the burner. The unit measures 18 inches in length, providing ample size for most standard installations. As part of Lochinvar's commitment to quality and performance, this burner assembly has been designed and manufactured to meet high industry standards, ensuring reliable operation and longevity.