This mantle helps prevent vapor condensation in the upper half of a flask during distillation of high-boiling materials. The tops are designed for use with Series M, TM, or STM mantles. They protect the flask, the solutions, and the laboratory in these ways:
1. from drafts, which would disturb the reflux ration during fractionation;
2. from flying glass of flask implosions in high-vacuum distillations;
3. from falling objects
4. from thermal strain between top and lower half of flask during high-temperature operations. With a glass-fabric construction and laced-side opening, the elliptical hole accomodates 1, 2, and 3-neck flasks.