Wilkins 3509-300B | #2 Check Assembly for Backflow Preventers, 2.5"-4"The Wilkins 3509 300B is a complete #2 check assembly designed for 350 350A 450 double check valve assemblies and 375 375A 475 475V reduced pressure backflow assemblies. This Zurn 3509 300B replacement component ensures reliable backflow prevention performance. Key Specifications: Size: 2 1 2 Inches to 4 Inches Temperature Range: 33F to 140F Body Material: Rubber and Steel Component Type: Complete #2 Check Assembly NOTICE: Do not use with water that