Heavy wall round bottom vessels have an internal thread for use with a 15mm Teflon Bushing as a pressure seal. This unique design allows hand tightening and losing for easy access into the vessel. The O-Ring is positioned on the Bushing above thread for improved sealing. The vessels are useful for pressure reactions and applications such as polymerization and analysis of halogens by thermal decomposition in the presence of time. Complete apparatus is supplied with vessel, Teflon Bushing and Viton O-Ring., TLG CS-P0170004 Pressure Vessel, Heavy wall, Round Bottom Vessel, Capacity 150mL, GL Thread 25