PYREX® Stoppers, Hollow-Blown Glass, 'C' Length, Hexagonal Top, 10/13 Ground Joint, 20 Pack

Stopper taper complies with ISO 383, Manufactured from 3.3 expansion borosilicate glass complying with ISO 3585 (ASTM E-438 Type 1 Class A), Hollow-blown construction to reduce weight, Hexagonal head prevents the stopper from rolling and provides good grip, Top of the stopper is flat or slightly concaved allowing them to be stood on end to avoid contamination of the ground surface