Review on Deluxe Wine and Beer Testing Kit: Ubrewusa's All-in-One Fermtech Hydrometer and Test Jar with Thief by Troy Jennings

Good for what it is. If you put this in a bottle that isn't filled to the brim, you'll end up with a tube barely half full. This means you can put your hydrometer in the middle of the pipe and not take it out to check your gravity again. If there is foam and the hydrometer is sticking to the wall preventing you from getting a reading, you will need to drain it and then invert the tube to remove it. Having to do this multiple times to get the right testing conditions means one of two things: 1- you either throw away what you have so you can have a little self-brew every time you test; or 2- They dump it back into the fermenter which could introduce contaminants. Might work with some people, but make sure your process takes this into account.