Looking for a type of comp. board

[cterrebonne]

I figured someone here would know what I am talking about. It's some type of composite similar to foam. It usually is tan in color and works great with poly resin. It has really good insulation properties and I have seen guys use it to make ice box to trawl boats after then coat it with fiberglass. It is used on my boat allready where the splash well by the last person to repair the transom.