Update to this good review after 2 months of use or so- make sure you do not exceed the FILL LINE. If you do, pressure builds up inside and there can be a gasket leak. This is NOT a product fault; it is USER ERROR. I had this leakage happen a couple of times but now I am more careful and there are no problems! I use frozen fruit, and I think when it heats up during blending it expands. Here is my original review: My original Ninja Auto iQ "Nutri Ninja Pro" blade assembly was about 5 or 6 years old and had started to leak black goop on the drive side. I still have to clean out the hardened goop from the main body of the machine- I had not noticed that it was slowly deteriorating. As they say, "it didn't owe me anything", as I use it pretty much every day to make breakfast smoothies, and five years lifetime is great. This replacement is super sharp, fits perfectly, and after two weeks of use I am super glad that I got it. Also, this may be my imagination, but it seems like it screws onto the plastic cups easier than the old one, which I often had to try to not cross-thread. Very satisfied and I recommend it. Replace yours before the black goop leaks all over your counter and hardens in the machine and is a pain to clean.