Floor Drain trap Seal, 3-1/2 in., Fits floor or shower frains with 3-1/2 in. stainter. 51 GPM flow rate. Working pressure 14.2 PSI. Minimizees evaporatin within the trap. Prevents sewer gases from escaping into the room and helps to mitigate back flow. Seall opens to allow the flow of drainage and closes when there is no flow. Aleternative to a trap primer elimnating the nee to pur water down the drain. Quick and siple installation - no special tools needed.