Tubeless tire tech is great. But sometimes the sealant can get in the valve core, dry up and leave a goo vaguely reminiscent of that gum stuck under everyone's desk in elementary school. It’s impossible to get off, but you don’t need to throw out the whole valve stem. Just get a new valve core. They’re pretty close to universal, but we know for a fact these will work with Stan’s valves, I9, WTB, Whiskey, Problem Solvers… Pull the old core out with this Park Valve Core Remover, and stick a new one in. This is a good little nugget to take with you on long tours, as it weighs nothing, and can be useful when bartering for slim jims. No wait. It can be useful if you pull your valve core out on the trail, lose it, and then have to try to fashion a new one using your roommate’s nose ring. We say: get 2 for your workshop, and one for your travel tool kit.