I started out using these by validating their markings using distilled water and something isn't right. For both of these, they appear to have been marked using a height gauge or something similar and I think that's ok. What I'm having trouble with is the fact that both of them appear to be out of spec by about 1.5mL - I have to add 1.5mL to get a full 500 grams, so the flask is technically over-full. I marked the 500mL level on the neck and then proceeded to further validate it using a non-electronic triple-beam balance and I got the same result. So, two different balances agree that the marking is wrong and I've done the validation in two different directions. In one case, I started with the Ohaus SPX2202 and filled the flask to 500 grams. This agreed with the mark I put on the neck earlier. I then emptied the flask into a beaker on my Ohaus 700 series triple beam balance, stopping at 250 grams twice over to get to 500 grams. Both balances agree with each other - both flasks appear to be incorrectly marked.

I can still use them, I just can't trust the markings on them until I figure out why this is happening. Maybe gravity is less here than it is elsewhere? Will keep an eye on it and post an update if an explanation appears.

Update: I calibrated my SPX2202 using the Ohaus calibration masses and I still get the same result. Worse, I've also checked this with another electronic balance, and the factory marking is still incorrect. If you are keeping score, 3 different balances (one of them calibrated to a standard) and all of them indicate that these are not within specification. I can't explain it. I've never had this issue with Karter Scientific products previously.

came well packed. is exactly as presented. high quality

Wonderful product! Will buy more later for sure

I have been teaching chemistry for 27 years. These volumetric flasks fit the bill for teaching students how to make diluted solutions! The flasks were perfect quality, arrived well-packaged and are perfect for my classroom needs.

I'm only using this item to hold fake flowers for a wedding centerpiece so I can't speak to its durability with everyday lab activities, but I did drop it on my vinyl floor from about 4 feet high and it didn't break. The glass stopper arrived with a crack which is why I'm only giving this item 4 stars.