StonyLab Solid Rubber Stoppers, 5-Pack 8# White Tapered Lab Seal Rubber Stoppers, Fits StonyLab 500ml Erlenmeyer Flask

The quality is nice - they don't rip, break, or tear. They so far haven't deteriorated from outside weather. I used them to plug holes from a previously installed ladder next to my pool. The plugs fit the ladder holes and the associated water line hole. I have also used them to plug the top of my umbrella stands during the winter while the umbrellas are stored. And i use them as bottle stoppers.There are quite a number of sizes available and it's easy to trim to meet the need for an in-between size.

Perfect fit for 2000ml erlenmyer flasks

The color? Pretty white. The shape? Conical frustum. The texture? Tough, but not too tough. I suppose, then, it's the function. Since they're stoppers, I've waited for them to stop, but they just keep going and going and going. That's probably a good thing, since it wouldn't be good if they'd stop stopping, but since they don't actually stop, it's just one of life's ongoing quandaries. Maybe I'll buy some more and see if they've finally stopped. What do YOU think?

Very solid. Unfortunately I did not realize that they are NOT food grade. Hence I have to use them with saran wrap as stoppers for my carboys.

Good value & shipped fast. Very much appreciate that the measurements of each size were provided which made it easy to find exactly what I needed. Thankyou!

Not fit for a lab setting. Not deflashed and covered in a grainy residue. I didn't need them for a lab setting and only needed one - which had taken me three tries to finally get the right size - so I deflashed and finished one by hand.

Use these with my plastic carboys when making wine.