Review on 🚴 Bike Tubeless Presta Valve Stem Kit - Super Light Alloy - Tubeless Valve Stem with Valve Core Remover Tool & Alloy Presta Valve Stem Caps - Available in Various Sizes (Black, 44mm) by Raysean Forth

I had trouble getting a full seal that included new rim tape after installation. I kept guessing the tape and repeating it a few times. I then tried stems with and without O-rings. Eventually I found that the neck of these valve stems is too wide. The Presta specification is the 6mm diameter marked on the threaded part. But right in front of the rubber stopper, they have a small gap - 6.6 mm. The hole in my rims is 6.5mm so they don't fit properly, the rubber can't be pushed into the rim of the hole. I managed to wash it out with Stan's sealant and it kept the air in, but it only lasted a week. I bought another brand which is 6mm correct and it sealed perfectly straight away and there were no problems. It's a shame because they've been good for my bikes and otherwise seem well made. The tool that comes with it is good and I still use it.