Stoppers are used with laboratory glassware such as flasks and separatory funnels. PTFE has excellent chemical resistance and resists freezing in ground glass joints. Remove the colored polyethylene handle from the PTFE stopper before cleaning or exposing to temperatures above 80°C. Stoppers of sizes 9 through 22 are solid, and sizes 32 through 38 are hollow. Designed from ASTM Specification E675.