Zurn Wilkins 1" 350XL Double Check Backflow Preventer. Product Details Top-mounted test cocks allow for easy installation EZSwap® pressure vessel reduces repair time and costs Flush Tool (FLUSH) provides easy line flushing, saving up to 15 minutes per installation Construction offers corrosion-resistance and winterization Low-lead law compliant ASSE® Listed 1015 IAPMO® Listed CSA® Certified B64.5 AWWA Compliant C510 Approved by the Foundation for Cross Connection Control and Hydraulic Research at the University of Southern California