Product review (4 stars): YouTube is a better source for installation instructions
Only four stars because the installation instructions could have be clearer and there are better ways to do it.

First, the instructions note about the coupling being reverse threaded should be bigger. This isn't the first time one of these coupling broke on me so I remembered it was left-handed thread and just had to scan the instruction sheet to confirm. But I know a lot of DIY guys out there aren't going to be reading the instructions carefully.

Second, the suggested method is just to pry up on the coupling. Essentially they want you to rip the old coupling straight off. Why they don't just say that I don't know. Now, you can do it this way with minimal fuss because the coupling's threads are much softer aluminum than the blender's steel threads. Just seems like a brutal method of surgery on your wife's nice blender. Don't forget to clean the threads. I saw on YouTube a method of use a mallet and a screwdriver to hit the coupling so it spins in the direction of 'off' i.e. clockwise. A couple of swift taps and the coupling spins right off.

Lastly, some businesses mark this as "special handling required" when shipping to Hawaii or Alaska. Seriously its rubber and plastic and will fit in a small padded evelope that the US Mail will gladly deliver. Some vendors are too cheap/lazy to deal with shipping outside the couterminous United States. Look around. You can probably find another supplier.