The Forespar Performance Products 903016 is a Forespar MF 844 Vented Loop for marine systems with a 1" barb size (25.4mm). Constructed from Marelon, this loop measures 7" (177.8mm) in height and 9" (228.6mm) in width. It is designed to prevent siphoning between tanks in marine toilets and engine cooling systems, featuring a one-way duckbill valve for effective sealing.