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

I bought this to do yeast starters for beer brewing and it's perfect. I used on direct flame to heat up and then chilled directly in an ice bath, as I have done with my other Boro 3.3 flasks and there were no issues. The bottom is flat, which works perfect with a stir bar/plate. I would recommend to anyone looking for a quality flask.

The media could not be loaded. 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.

It's a good flask, the stopper works well too, not sure how it would fair against solvents though so it would be wise to ask the seller if that will be a concern. Aside from that, I can say it is borosilicate glass that is what you would expect from lab equipment. Sturdy and thick, no complaints here.

Got this to test my pool chemistry. I use the flask to collect the sample water. Works great for that.

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.

The glass on these is very thick and should stand up to years of use. The stopper is airtight and holds my airlock fine. I use these for yeast starters and yeast "ranching" various cultures. Highly recommended.

When people ask why I have a flask with me I tell them it’s because you never know when you might need to make a potion.

As someone else noted, the stopper for the smallest flask is undersized, so pushing it down even slightly would force it right into the flask. Odd that this hasn't been corrected yet, or that nobody even bothered to check if it fit before selling it.

Parece buena calidad, para escenografía asi que no se le dio uso real

Glass ok but the stopper is too small and falls inside, should have paid the same price and got a better quality product without a stopper.

Great value

I'm buying more

The smallest cap is bigger than the smallest glass so it doesn't fit.