Review on 🚴 Presta Valve Core Bike Replacement Brass Tubeless Core - 20 Pieces for Road MTB Bike, Compatible with Stan's, Vittoria, Continental, Kenda, Mor by Issac Burnett

Product looks good and high quality. However, the product I received was defective when I used replacement cores with Continental tubing or valve extenders. I use a 40mm Continental Presta valve extender with 48mm Continental hoses. When I used the replacement core that was ordered, inflated the tire, then loosened the valve tip, pushed on the tip to deflate the tire, no air came out of the valve. I tried five new replacement cores from this order. All have failed. I then used a core from a new Continental tube. It worked fine as usual. I also installed the replacement core directly into the Continental hose valve. This also failed. This led me to conclude that the product was defective or not compatible with Continental pipe valves or valve extensions. The problem was the misalignment of the black rubber grommet on the bottom of the pen. The seal is fixed with a groove. This seal prevents air from escaping from the tire when the valve is closed. When the valve is opened and the pin is pushed down, the seal is also pushed out along with the pin, allowing air to be expelled from the tire. However, inspection of the defective replacement cores revealed that the seal had come loose from the pressure groove in the tire, pushed up and blocked the valve air passage when the valve was open. The gasket was also wider than the Continental OEM.