I hate it when you open up the instructions and find out you have to go shopping before you do the trick. You need 2 more things before you can set it up, one of them is a common magician's material (which I didn't own) and the other is something you can find in every supermarket.
The gimmick has a fault that makes it look bad at a large section of the bottle. Dealing and setting it up is messy and when you're done it just doesn't look that good.
I sold it to a fellow magician 2 days after it has arrived.

I see that there is a pretty negative review, so I thought I would chime in. I have one and I am very pleased with it. I understand it has it's limitations. This is not for close-up work. It is noticeable at close distance. However, it is beautiful for stage work. I also like to use it just goofing off at a restaurant. I always like to have a little something to just flip people out. I take it to a restaurant and if I see someone at another table looking over, I start to drink the soday out of my ear. It is hilarious! For what it is, it is really a cleverly made device. I still can't see how they managed to make this thing. As for the extra items needed, it would have been nice if they included a bit of magician's wax, but it is no sweat. If you decide to buy it, just also buy some magician's wax from Penguin, or you can use adhesive dots that are readily available at most any office supply store.
I highly recommend it for the right use.

Despite following all the instructions and making the liquid darker using the extra bits required, there must be a leak somewhere as the bottle start the emptying effect without my control. Useless

Trick was horrid because the bottle was inferior. I had to add black ink to it to darken it up and still it had streaks where it did not flow to the bottom. I hope no one else wastes their money on this crappy bottle.

Did not work well. Had to add black ink to make it dark enough and then it still had holes as it dripped down. Don't waste your money on this inferior bottle.