Stanchion backing plate, stainless steel, for trapezoidal base. Sometime around 1990 the hole pattern for Catalina's stanchion bases changed. The hole spacing is slightly different (by about 1/8" center to center) than newer stanchions. This is the plate for newer boats built after that time and for all new trapezoidal based stanchions with a vent purchased from Catalina Direct.
Overall dimensions: 3" X 4"