Water resistant and prevents ingestion of water into fuel tank under normal sea conditions and wash down. Baffles and traps allow air movement. Eliminates need for anti-siphon loop and requires less hose for installation. Meets ABYC H-24 ventilation specs and will fit hulls 1/16" to 9/16" thick. Installs easily and permanently. Made of flame-retardant plastic. For 5/8" ID hose. Installation hole size is 3/4" ID.