The 1 1/2" Watts Series 800M4 is a pressure vacuum breaker (PVB) began production in 1994 and is still currently being produced. It features a bronze body with plastic internal parts. In 2010, A lead free version was introduced, which is tagged LF800M4. "Lead free" models use the same internal parts as the "leaded" versions. A "freeze resistant" model was introduced in 1995 and was tagged under the 800M4-FR. Some repair parts are different for the FR, so please be sure which model you have before ordering parts.