Natural, unbleached 8 oz. cotton duck is stretched around specially designed, kiln-dried stretcher bars, and held in place with a flexible spline allowing these canvases to be painted on all four edges as well as the canvas surface. The surface is triple-acrylic primed, acid-free, and staple-free on the sides. The Studio canvas features a 7/8" edge, while the Gallery canvas features a thick 1-1/2" edge. They are suitable for oil and acrylic painting.