The 426 Series Check Valve promotes multiple configurations to fit the exact end use application. Gray PVC with 1 psi stainless spring and ball is the standard configuration. PVC is a NSF Standard 61 Approved Material. Nylon, PVDF (Kynar®) and Glass Filled Polypropylene are available for chemical resistance applications. MakroBlend is an NSF Standard 51 Approved Material. Hastelloy is a superior chemically resistant spring material. Teflon® balls are standard with Hastelloy springs for chemical resistance applications. Options are available by special order with a minimum order of 100 units. Please call us at 877-335-3339 to place a special order. Material Options Gray PVC (Standard), White PVC, White Polypropylene, Black Nylon,White Nylon, MakroBlend, Black PVDF (Kynar®)Seal Options Buna-N (Standard), Ethylene Propylene, Fluoroelastomer (Viton®)End Options 1/8, 1/4 Male and Female NPT1/8, 1/4, 5/16, 3/8, 1/2 Hose Barb1/8, 1/4 JACO1/4, 3/8 SMC Push-To-Connect3/8 BIB (Smooth Barb)Cracking Pressure 1 psi (Standard), 1/3, 1.5, 3, 5, 7, 10, 12 psi or No Spring, Hastelloy Spring - 1/3, 1, 5, 12 psiBall Material 316 Stainless Ball with 302 Stainless Spring (Standard), Teflon® Ball with Hastelloy Spring