These graduated flasks have a heavier wall than standard Erlenmeyer flasks, and can withstand 1 atmosphere, or vacuum to 29" Hg. Tubulation OD for flasks from 25- to 500-mL capacity is 5⁄16". Tubulation OD for 1000- to 4000-mL flasks is 3⁄8". Compliance: ASTM E 1406, Type II, Class I. Temperature range: 840°F (450°C) max.