Since it was developed almost 50 years ago by our founder in our own R&D facility, the Spirovent® remains the world class industry standard that others attempt to reach.  Often copied but never equaled, tens of millions have been installed worldwide.  It is recommended and installed by the best plumbing and heating contractors for highly efficient and quiet hydronic heating, radiant, and solar systems.  Stocked by the top wholesalers throughout North America, it is readily availiable in all geographic markets.