Park Tool VC-1 Valve Core Tool
A valve core tool should be in every toolbox. Use it to check that your valve cores are tight, or to remove them and add a little sealant to your tubes.
Most modern tubes have removable valve cores. You can unscrew the valve core and put a little sealant (we recommend Stan’s) inside the tube. The sealant will close small holes just like it does in a tubeless tire, but you avoid having to seat a tubeless tire.
Sometimes, the removable valve cores aren’t screwed in tightly at the factory, and they slowly leak air. It even happens, albeit rarely, with the high-quality Schwalbe tubes we sell. Use the valve core tool to check your valves before you install the tube. That way, you know that if the tire is leaking air, it’s really a puncture, and not just a loose valve.