Patented EZ-Valve® system from Paper Systems (Des Moines, IA) consists of a reclosable valve heat-sealed to a bulk container liner. Both components are made of PE that's FDA-approved as a food grade material.
Shrink wrap is placed around the valve to assure tamper evidence. The valve measures 1 1/2" dia. Inbound side is 120% larger for positive flow. Can be used with most bulk containers.