United Scientific RSTPK4 Rubber Stopper, 2 to 8 Sizes Assortment, 2-Holes

These RSTPK4 Rubber Stoppers, Sizes 2 to 8 - Assortment each has 2-Holes for your tubes from United Scientific and are sized from a smallish #2 which will fit into the hole of a wine bottle completely and won't come out easily, has a small end smaller than a dime (16 mm), #3 whose small end is larger than a penny (18mm) and is even harder to get along with around a wine bottle and a #4's small end is about 20mm and top is 26mm, and this was the first I measured both top and bottom for slope comparisons. #5 is a doosey, in that it is reversed, with the bottom being larger than the top, at 27mm and 22.5mm, strange huh? #6 is the sad sack of this sack of stoppers and is 26 and 31mm. #7 is the sweet one that will probably never get taken advantage of with a measurement of 29-33-37mm. Woowoo! #8 is just boring at 32 and 40mm and as with the others, has two holes for 1/4" tubing.The bag contained 27 stoppers, and I'll let you guess which # it had the most of. Contest rules will determine the winner, based on likes and dislikes of this review. Occasionally I'll go over board on my reviewing, but when I started this review I guess the smell of the black rubber just was too much for me. With the holes and all, I would say just plug them if they are not needed. In the lab, these stoppers are invaluable to the nerds who work there. Oh, I know they are, but what about me. These stoppers are Good quality, just not as good as Silicone stoppers, but cheaper and at a List Price: $16.20 where you pay only $11.79 ($11.79 / EACH bag) and free Shipping for Prime Members, I'd say it is well worth if for 27 stoppers. There are fewer of some than others. You Save: $4.41 (27%) off the price of them Retail, as listed. So, go for it if you are looking to buy one stopper, as I was and was willing to drop the cash. You and I are sad!

I use these for utility purposes, their rubber stoppers, not much to rave about

They're rubber, they're stoppers, they have two holes. What else could you want them to be. There are a couple of each size included. I use them to insert 5mm glass tubing, a nice snug fit and seal.

Good Quality.

Got these in and had a ball showing the kids various ways that they can be used in science apparatus set ups.

...good

Excellent double hole rubber stopper.

Right on.