These cylindrical, heavy-walled reaction vessels are fabricated from borosilicate glass to accommodate immersion wells. Open-mouthed models facilitate the introduction and removal of materials and allow for easy cleaning. Wall thickness is uniform. Flat bottoms in some models allow use of magnetic stirrers. Cylindrical vessels are durable in design and easy to use, and flasks are suitable for vacuum operation. Flat-top edges in some models are compatible for providing a leak-proof fit with certain lids.