Borosilicate, with penny head Conforms to ASTM Standard E 675 Size Standard Taper 13 has solid plug; size Standard Taper 38 has recessed bottom Standard Taper designation indicates the approximate diameter of the ground zone at its widest (gauging) point.

Stoppers are used with laboratory glassware such as flasks and separatory funnels. Sizes Standard Taper 10/30 through Standard Taper 19/38 are solid Manufactured from 33 expansion, low extractable borosilicate glass conforming to USP Type I and ASTM E438, Type I, Class A requirements

Stoppers are used with laboratory glassware such as flasks and separatory funnels. Sizes Standard Taper 24/40 and larger are hollow Manufactured from 33 expansion, low extractable borosilicate glass conforming to USP Type I and ASTM E438, Type I, Class A requirements

Hollow plug type With sealed bottom and vertical penny head