Flask, Round Bottom, 3000mL, Heavy Wall, 24/40 - 24/40, 10/30 Thermometer Joint, 4-Neck. Round bottom, HEAVY WALL, four-neck flask with standard taper outer joints on the center neck and vertical side necks. The third neck is a 10/30 outer joint for use with a CG-3506, 10/30 jointed thermometer.