TLDR: One of the two valve extenders in the pack I received is defective. When I screw a valve core all the way into it, the valve core is still loose and won't seal properly (see picture - the valve core angles up when I push on it).Longer Explanation:I installed both of these valve extenders using brand new tubes (and their valve cores) and when I attempted to fill the tires with air, the front tire didn't seem to want to fill. Note, I am using them with Continental Race 28" 700x20-25c tubes (80mm presta valve and removable valve core), along with Continental GP 5000 tires in case anyone cares. I would attach the pump and start pumping and though it appeared there was a seal, the pump gauge would go from zero to over 120 psi with no air going into the tire. After removing and reattaching the pump repeatedly I got air to go in slowly, but I could only pump about once every 5 seconds. I managed to get the tire to 90 psi and went for a ride, but I noticed the tire was flat 24 hours later. I also noted that the rear tire was holding air when I checked several days later.Once I had time to troubleshoot further, I removed both valve extenders (leaving the valve cores screwed into them) and swapped them extenders/cores between the front and rear tires. This time the rear tire had the issue. I could only fill it slowly and it went flat in a couple hours while the front tire hadn't lost any pressure when I checked it days later. This confirmed that there were no leaks coming from either of the tubes.The last troubleshooting step was to leave the valve extenders in place and swap only the valve cores between the front and rear tires. When I did this the issue happened again with the rear tire. This proved that both valve cores worked correctly (when used with the functioning valve extender now on the front tire). Thus I was able to isolate the valve extender on the rear tire as the source of the problem.I removed the rear tire and got out a magnifying glass and tried to observe if there was any noticeable issue while screwing the valve extender into a valve stem, or while screwing a valve core into the valve extender. I found that when a valve core is screwed fully into this valve extender (to the stop as tight as possible using the provided tool) the valve core is still loose and I am able to wiggle it off axis (see picture - the valve core angles up when I push on it). It seems the threading of the female end of the valve extender is too large to receive the threaded male end of the valve stem, thus preventing a seal. I tried this with three different valve cores from three different Continental tubes, and all had the same issue. I also tried all three valve cores on the good valve extender in the pack and all seemed to fit normally without any wiggle.So, one of the two valve extenders in the pack I received is defective.Unfortunately, I figured this out five days after the return window closed, so I'm unable to return them. I attempted to use Amazon's troubleshooting options, and I followed a link to Continental's website but was unable to find the product or any customer assistance. I couldn't figure out how to contact the seller directly about the issue, only about a return, and the automated chat bot told me I was past the return window and ended that option. So with no help from the manufacturer, seller, or Amazon, as of right now I'm just out the cost, along with several hours of removing and swapping tires, tubes, valve extenders, and valve cores to troubleshoot, not to mention not being able to ride my bike for the last month.

Perfekte Ventil Verlängerung. Hat bei mir super geklappt und hält perfekt dicht. Der Druckverlust ist genauso mit Ventilverlängerung wie ohne in der gleichen Zeit. Klare Kaufempfehlung.

No problems if you have a removable valve core, on time to boot

Parfait pour mes jantes hautes. Livré avec petit outil demonte obus

I found this very easy to install when you follow the directions. I've used the extender on two tubes. For both tubes, the fit seems correct however when attempting to pump up the tire I meet extreme resistance. Pressure gauge on the pump shows inaccurate results and makes adding air very difficult.

I was looking for an extender for my presta tubes. This was not it.

Done the work very well!Fit on snug! No leaks at all! Though I did add some TPFE tape for extra protection.The Little tensioner was a great bonus

Pratici ed indispensabili se le valvole sono cortine

I appreciated finding these for a good fair price. They do what they are supposed to do and they are much better than other options like the "silca" valve extenders which can get stuck inside the valve port of some wheels (like my flo 60 carbon wheels)

Si necesitais prolongadores estos si son los bueno muy buena compra apretan muy bien y se queda el obus perfectamente agarrado sin ninguna perdida de aire buena compra

Originally, I just tried screwing one of these puppies over the presta valve of a tire on an aero wheel, but that didn't work well at all. Prepared to award this seemingly miserable product a single star and a nasty review, I happened to glance at the DIRECTIONS, and realized the valve was to be disassembled BEFORE attaching the extender, and that the black plastic piece in the packaging was a wrench intended to accomplish this very purpose, and not, as I initially perceived, a roach clip misplaced by a Continental or Amazon employee. This is a great product that works wonderfully, even if the wrench looks like a piece of drug paraphernalia.

OK, so this is my second set (and third) of these continental valve extenders. Honestly, the third set is just a spare in the event that for some reason I need them. I have found that too much is better than not enough.I purchased the first set after I received my deep rim wheels from Flo (I dig these wheels and for the cost, the are quite nice). Flo sent me a set of Silca valve extenders, which broke during set up. I was really disappointed in them and became really disappointed that I couldn't use my wheels the day they came. I did a little research and ordered these.Install was quick and (even though Silca is just a one step process and this is three) this was an amazingly simple install.Rode these for IM Austin 70.3 and had no issues (except a nervous mistake prior to starting in which I flattened the tire by unscrewing the extender). I don't seem to have any air leaks, not any of significance anyway.

Works very well for my FLO wheels. Great for Deep dish wheels. Durability so far works very flawlessly. Put close to 1000 miles on them with no air leak. I recommend using Teflon tape to make a greater seal where it screws on. Recommended