These Pyrex gas washing Standard Taper stoppers are replacements for the 500mL gas washing bottles (No. 31760-500EC). Sidearm tubulations are 8mm O.D. A 40/50 Standard Taper stopper is used to seal the top to the base. This Standard Taper stopper incorporates a tube with a 20mm diameter extra coarse fritted disc as the distributor. The fritted disc provides greater efficiency and more uniform dispersion of gas bubbles for complete absorption. This extra coarse frit has a nominal pore distribution of 170 to 220µm. Please check the Guide to Selecting and Using Fritted Glassware in our Technical Information Listing for additional information on fritted ware.