Features•  Uninsulated• Tested to withstand 20'' W.G. positive pressure & 10'' of negative pressure• Closed cell neoprene gasket• Bonding of neoprene gasket to inside plate prevents leakage• Conical springs between the two plates provides for easy installation• High impact plastic knobs are designed to avoid stripping and allow a tool-free operation• Template for duct-opening cut out insures proper hole size