250ml Narrow Mouth Erlenmeyer Flask with Rubber Stopper, 3.3 Borosilicate Glass, Karter Scientific (Single)

Nice set. Thick glass. It’s exactly what it says it is. The rubber stoppers fit perfectly. I only wished they had the defined shape as the older flasks.

Perfect

Overall I am satisfied with glassware. Aside from very minor imperfections and finding a large chunk of glass in the 250ml (which scared me as I thought the flask had broken during transit... luckily it was from an unknown source), the glass arrived quickly and as described. The #2 rubber stopper on the other hand was less desirable. The larger stoppers fit well but upon dropping the #2 into the top of the 50ml, it sat down unusually low. I gave the stopper a little press downward to check for a seal (and I'm talking very minimal pressure) and instead the stopper just slid down inside the flask. Perhaps the stopper decided to resize itself correctly once inside the flask (lol) as attempts at retrieving it were futile. That said... I'm still giving a rating of 4 stars, as the set, even minus one, is an amazing deal. Edit 10/20: And 5 stars it is. Thank you Amazon for being amazing and making it right. Never dissatisfied with Amazons customer service.

It’s great that you can buy just one, comes in a nice box, and mine came unbroken. Sometimes you have to buy them in packs of six to ten and last time I needed flasks I actually got them from a science department throwing them out. It’s glass, glass is not suppose to readily accept substances into its silicone matrix, but I was still told to be careful. At this price point, I get one new flask that has never been used before. The flask got washed out and dried before using. It does not claim to be a Pyrex flask which can take an array of chemical assaults before possibly breaking but I am using it for a colder temp mixing experiment, not freezing, and if cooled properly, most glass holds up just fine. Anything I would earmark a Pyrex flask for I would probably not do at home anyway. Mixing dyes and even summer drinks like fruit punch, flasks are a go to, especially with an electric magnetic stirrer. Yes you can wow your friends mixing instant fruit drink with a flask and magnetic stirrer. Just be sure to take the magnet out of the drink. The best thing is I could buy just one. The stopper also fit.

The look and feel of the equipment is good. However, only one of the stoppers fits properly in one of the flasks. In the smallest bottle one of the stoppers falls in, another is too big to fit at all, and the third stopper gets snug as it becomes flush with the top of the flask. (very difficult to remove) The two smallest stoppers fall inside the two larger flasks. The middle flask is actually larger mouthed and the largest stopper nearly falls to flush in that flask as well. The largest bottle has the second largest mouth and fits the largest stopper well. Unfortunately this leaves two of the flasks without stoppers. As well as two stoppers that make great floats. Of course your mileage may vary. According to the size chart on Sciencecompany.com this set should have been shipped with sizes 5, 6, and either 6.5 to 7. Not sure of the size for the largest flask. I think either might work for the largest mouthed flask. Quick update: I have been doing a little research about these flasks, Karter Scientific 214U8 and the reference set listed on Amazon without the stoppers Karter Scientific 214U2 indicates the mouths of the flasks as follows: 50ml: approx 17mm, 150ml: approx 22mm, 250ml: approx 25mm. These numbers are not accurate for the set I received. The mouths were instead as follows: 50ml: approx 26mm, 150ml: approx 31mm, 250ml: approx 28mm. If the flasks were sized as described in the Karter Scientific 214U2, I believe the stoppers that shipped with this kit, would, in fact, fit correctly. So I do not know which is wrong but now suspect I was sent the wrong size flasks, or the flasks mouths have been redesigned to be larger, but the stoppers that come with them were never switched to larger sized stoppers. Don't know which, but clearly something is rotten here.

As expected. Perfect for my yeast starter. I use it with magnetic stir plate. Works like a charm. No complaints. Clear, labeled accurately, stopper fits, great priced flask. I verified measurements are accurate. Spot on.

Just as it should be. I just use it to store coffee concentrate after I make it and I can pour the concentrate in at any temperature without worrying.

Like it. I use it to emulsify my fermented hot sauce… was recommended by the Chili-Chump on YouTube…because it has a large flat bottom for the stir plate. At first I resisted but broke down and I’m happy I did. Bought 2. I also use them to make Margaritas… and in conjunction with the magnetic stir plate with the gear wheel… primarily having the stopper on while it stirs… and not having “napalm” hot pepper burning my eyes… well worth it. Try putting a stopper or cover a standard flask beaker quickly and easily with one hand… 2000ml is larger and I use two hands to swirl or shake if needed.