I already have some of these laboratory stoppers in larger sizes. I find them useful as paperweights, for hammering when I don't want to damage the item I'm hammering, and as isolation feet to reduce noise or vibrations from machines or speakers, as well as sealing jars or tins temporarily.This size is 48mm / 1.88" Bottom Diameter x 56mm / 2.16" Top Diameter x 25mm / 0.98" High. The item page is a little confusing, they look smaller (less wide) than they actually are, and the measurements on the item page are a little wrong, the top diameter is 56mm, not 26mm. I think these are size 11 stoppers.These are well-priced, strong, and last a long time. Although they're silicone rubber they feel and smell like natural rubber, the smell wears off after they've been used for a short while. They're quite heavy.I find this size useful for all sorts of things, they work well to temporarily seal jars and tins. Shown in some of my pictures is one used to seal a medium-sized glass jar, for reference, the jar is an old olive jar that's a little smaller than a regular jam jar.They're handy to keep around to use as paperweights on my desk too, or for holding items in place for cutting.Overall, they're useful, practical, resilient, long-lasting, and versatile, as well as being reasonably priced, excellent!

So these are marketed as Test Tube bungs and they will definitely work for that purpose, the taper means they should be relatively easy to install, provide a decent seal and then be somewhat simple to remove assuming you don't leave them in for extended periods...I picked them up so I can create some new woodturning jigs for my workshop as the taper means they will create a decent grab when tightened using some home made chuck jaws and these bungs threaded in to some t-nuts... Home-made Cole jaws or a future project to make a Longworth chuck to help hold my biggest bowls...Overall, these represent great value for money. Happy to give a thumbs up 👍

Made from Very hard rubber and fits the top of the Beakers well.