The neck of the flask is 0.5" outside diameter. The base diameter of the flask is 0.9" and the overall height is 3.2". Please note: these are hand blown with the capacity in mind and overall dimensions can vary slightly. Hand blown, Class A premium borosilicate 3.3 glass. The stopper is socket size 10/19, made of polyethylene, and is acid proof and autoclavable. Designed to measure and store liquids in the laboratory, but can be used in the home as well -- or even in a set for "potions". Top rack dishwasher safe and autoclavable. Premium borosilicate volumetric Class A flasks with acid proof polyethylene stoppers. Eisco glassware is designed to be used in labs but is often used in homes or garages as well. NOTE: Polyethylene stoppers cannot be autoclaved. They have a temperature compatibility range of -40°C to +80°C. Remove stoppers before autoclaving the glass flask body.