Ace Reaction Flask Head w/ Thermometer Joint, model 651338 is manufactured by Ace Glass. This product is for use with reaction flasks, fits flask 2,000 - 4,000 mL. This head has three in-line joints and a #7 Ace-Thred, internally threaded side opening for thermometer (6 to 7 mm o.d.). The thread forms a compression seal with the bushing and allows vertical adjustment of the thermometer.