Across International DomeShield 800C Rated Fabric Insulating Top for 20L FlasksThe Ai ultra thick insulating tops will keep your distillation setup at the peak of its performance, they will help prevent vapor condensation in the upper half of a flask, at the same time, protect the flask, the solutions, and the lab 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