The 2" Watts Series 800M4-FR pressure vacuum breaker began production in 1995 and is still currently being produced. In 2010, A lead free version was introduced, which is tagged LF800M4-FR. The lead free and leaded versions use the same internal parts. The "FR" stands for "freeze resistant" and contains a small relief built into the air inlet float to prevent damage if frozen. Please note, this device is freeze resistant, not freeze-proof. This device should still be drained and winterized in freezing conditions. The valve features a bronze body with plastic internal parts. Check seats are replacable and thread into the body. No special tools are required for service.