The side of the potion flask the viewer potion sees looks too flat; it looks 3d, but as if that side of the flask is a flat-face; particularly in the middle/bottom of the flask; where the cork is the flask actually looks round, but lower, not so much. If the bottom end of the drawing of the flask was curved down more, not so horizontally level, it would look more like the nearest edge of the flask was coming out toward the viewer.