Auspex Scientific - The Exciting Science and Educational Store
Twist one of the three rubber protrusions off and the solid stopper becomes a one-hole stopper. Twist another one off, and have a two-hole stopper. Twist the last one off, and it becomes a three-hole stopper.
Made of "white" natural rubber, with safe, convenient, countersunk 5 mm holes.
Top diameter 32 mm
Bottom diameter 26 mm
Height 24 mm
5 stoppers per pack.