Almost all high-end mountain bikes now come with tubeless tires, which are capable of sealing small punctures if filled with a liquid sealant. The just-announced Dart tool, made by Stan’s NoTubes, is designed to better-fix the bigger holes.
Stan’s was one of the first companies to introduce a mountain bike tire sealant, and it’s still probably the most-used brand. The latex-based liquid contains small rubber particles, which block and then seal smaller holes in tires. For larger punctures – over 5 mm – riders typically have to utilize a third-party automotive-style tool, that inserts a worm-shaped sticky rubber plug into the hole.
The Dart tool likewise utilizes a carbon fiber rod to hand-push a polymer strip (called a dart) into larger punctures. That material not only fills the hole, but it also chemically reacts with the Stan’s sealant already in the tire, to form a seal that’s reportedly much stronger than that which would be created by a standard plug.