3 GALLON SIZE (smooth walls) P.E.T. CARBOY – (P.E.T. = Polyethylene terephthalate material) Designed for wine and beer makers. No BPA. Thicker walls for less permeability. Sediment or yeast will not attach to the walls. Flat base makes the carboy easy to clean with brush, adhesive thermometer can be attached to the outside wall.