Can anyone Identify this...thing?

This came as part of a physics lab.  Can anyone identify this thing and where I might purchase a duplicate should I need one?

It's approximately 1 1/4 inches long and has two holes running through the center.
It's made out of rubber.

Picture of Can anyone Identify this...thing?
gmoon7 years ago
Stopper for a flask, bottle, etc. The holes are for tubing (usually glass, if I recall). I didn't search, but I'm sure you can still buy them.
My local Ace Hardware carries them.
Oh great! I thought I was going to have to get these online. I'll check that out.