3 Neck Heavy Wall Round Bottom Flask - USA Made3 Neck Heavy Wall Round Bottom Flask USA Made This USA made 3 Heavy Wall Round Bottom Flask is designed specifically for Short Path Distillation units and allows dual distillation heads and cows so there is more vapor flow from the heating mantle. These flasks are made of heavy walled borosilicate. Specifications Material Heavy Wall Borosilicate Sizes Available: 10000ml 24 40 Center Joint and 34 45 Side Joints 20000ml 24 40 Center Joint and 45 50 Side