Nothing special other than it is a Hydrometer Jar, Plastic with a plastic base. The one I received does not sit flat on a table or surface, (not a huge issue, just take a razor and shave the bottom, a little bit). For the price, it works fine.
If you need something quick and don't want to spend a few dollars more for one of the other Hydrometer Jar's, this would get my recommendation.
I mean... it's a cylinder, so it works alright. The build quality is terrible though. The base is too short, so it wobbles all over the place, and the build quality is overall just rubbish. Worth a dollar maybe... total waste of money.
I've had this test jar for a couple months, and it worked fine until now. When taking a FG, I noticed that it was leaking. No amount of tightening, loosening, or wrapping the bottom with plastic wrap would completely stop the leak. While I like the 2-piece design, I wouldn't recommend this to anybody. Just get a 1-piece test jar, and save yourself the eventual messy countertop and waste of beer.
They both leak now but took a while...8 months of brewing every three weeks or so. At the beginning they were great. The problem is the material on the base is cheap enough plastic that heated wort will eventually warp it enough to cause a slow leak. This is a GUARANTEE. I'd much rather have a one piece construction but those aren't sold here anymore. Rather not have glass for obvious reasons.
This has worked well. Two piece construction means it is very easy to clean. It never leaks. quality is good and the plastic tube is extremely clear and easy to look thru to get a reading from your hydrometer.
While it is nice for cleaning to have the bottom screw off, mine leaks where the bottom screws on. It is a slow leak but significant enough that it forces me to check a gravity reading soon after adding to the jar.
Nice comprimise between 100ml and 250ml graduated cylinders, but please note it's a 2 piece. Tighten up the base before you take a reading. My first sample held for about 5 sec before dumping wort all over the place. It looks like the base is glued in place, but it is in fact a screw on. Plan accordingly.