The 360 Siphon RV holding tank vent cap eliminates odors from the source - the holding tanks - and exhausts them out the roof vent before they have a chance to invade the RV living space. By design, the patented 360 Siphon can only create an updraft, expelling odors and fostering an oxygen-rich environment to speed up waste breakdown. Breathe easier and enjoy a healthy, odor-free living environment with the 360 Siphon. Prevents odors and gasses from invading RV living space. Speeds up waste breakdown, eliminating the need for chemicals. Made in America of strong polycarbonate. Easy installation and universal fit. Built-in bug screen.