Round fiberglass dorade box fits 3" and 4" deck plates and vents.  This box can be used to house a mushroom vent and can be closed from the interior of the cabin.  Water entering thru your vent will be reflected off the mushroom vent and drained out the weep holes at the bottom of the dorade box.  Our 4" cast mushroom vent works togther with this box giving you ventilation without the worries of water entering the cabin. 
 
*Vent not included and is sold separately
 
Overall box diameter width 6-1/2"
Overall box height above deck 6"