I can't imagine this product was actually user tested. First you have to find a very small and hard to see arrow on both the base and the cup. Zero contrast, almost impossible to see. Then you have to line them up just perfectly and pray to the smoothie gods that the threads actually catch in that exact position. You put it in the Vitamix aaand... nothing, so you un screw, re screw aaaand... nothing again. Repeat several times and if you're lucky the Vitamix will finally register the cup and blend. Most frustrating product I've purchased in a long time, no way would I recommend. Also, there are two channels on the inside. Why the inside? We need those on the outside so you can actually get a grip on this wet and smooth cup to unscrew the base.