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 from drafts, which would disturb the reflux ration during fractionation, from flying glass of flask implosions in high vacuum distillations, from falling objects; and, 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.