Review on 6PCS Presta to Schrader Valve Adaptors for Bike, Convert Presta Valve, Inflate Tire with Standard Pump or Air Compressor, Includes 12PCS Tire Valve Caps by Bill Wieser

The adapter can therefore be screwed perfectly onto the Presta valve. The downside is that the diameter of the top of the adapter doesn't quite match. The supplied cap cannot be screwed on properly. Threads are not taken. I can take off my hat right away. Tried all the caps that came with it. Everything the same. But the problem is that everything is fine with the caps. I tried them on my old bike with Schrader valves and they fit perfectly. Then I tried screwing the old cover from my old bike onto these new ones. Same result. Wouldn't be a thread. Pulled it out right away. So the disadvantage is the thread on the top of the adapter. To keep the cap in place I wrapped tape around the adapter to grab and hold the cap. It worked. HZJD may want to review their performance.