Auspex Scientific - The Exciting Science and Educational Store
Twist one of the three protrusions off, and the solid stopper becomes a one-hole stopper. Twist another one off, and you have a two-hole stopper. Twist the last one off, and it becomes a 3-hole stopper.
Made of "white" natural rubber, with safe, convenient, countersunk 5 mm holes.
Top diameter 45 mm
Bottom diameter 38 mm
Height 26 mm
5 stoppers per pack.