This 30x40 size is in the 4:3 Cinema. Pure medium weight Belgian Linen finished to a primed weight of 12 oz.. It's double sized and double primed with archival quality acrylic gesso making the ground impervious to paints leaching through and harming the fabric. Suitable for most all paint types, like oils, acrylics, and alkyds. Linen is the world's strongest natural fiber. It has oils that keep it flexible and prevent disintegration over time. The surface has a characteristic linen texture. There is a 1/2" gap between the canvas and frame, eliminating the unwanted lines that occur when the gap is less. We never use finger joints in our wood frames, which often fail under tension and over time - the glue joints give-up, and are unsuitable for paintings intended to last for centuries. Patented 3.25" wide heavy duty keyable cross braces allow the canvas frame to be tensioned in the middle, where the tension is needed the most! The Stretcher Bars are slotted in the center to accept a cross brace. Due to our unique design, the cross braces provide maximum rigidity and may be removed, if desired. Both corner keys and brace keys are pre-installed. Stretched using our proprietary MuseumWrap method, producing a drum-tight-stretch up to 50% tighter than other methods, and with balanced tension across the surface. The corners are uncut and neatly folded, making it possible to remove and re-stretch the canvas on the same size frame.