PYREX? Stopper, hollow-blown glass, hexagonal top, ground 29/22 joint

PYREX? Stopper, hollow-blown glass, hexagonal top, ground 29/22 joint
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