Borosilicate glass, round-bottom vessel. Supplied with 24/40 center neck and two 24/40 side necks. Fourth neck is #25 Screw thread on 500mL for use with 7506-10 bushing and o-ring; #36 Screw thread on 1000mL and 2000mL sizes for use with 7506-12 bushing and o-ring to make a leak-tight compression seal with all 9814 horns and 9852-41 or 9852-45 slide adapter. Center neck can be used for mechanical stirring if needed. Stated capacity is WITHOUT horn. See horn selection chart, below, for proper horn size. Vessel NOT supplied with bushing or o-ring, order separately.