Love the product. Use them mainly for Triathlon races with aero wheels. A little confusing at first on the website with regards to Kit. Thought I had ordered a kit of different sizes. Instead, they come multiple in a pack of the same size. So had to buy multiple packages to get extenders needed for different size rims. Now I have a bunch of extras I probably won't ever use. They will go into my parts bag I take to every event in case someone else needs something.
I shopped around and there are plenty of valve extender pairs for around $20 so adding a third and some wrenches for only a few dollars more was a no brainer. I installed two in a pair of Vittoria latex tubes and the third in a spare (Zipp's Tangente road tube). Installation was simple (I used Teflon tape) and it holds air equally as well or better (because the tape) than the normal latex tubes. Highly recommend if you're in the market for extenders, mostly because it comes with a third so you can have one installed on your spare already.