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.
The company additionally claims that because the darts are softer and more flexible than regular plugs, they're better able to conform to the contours of punctures. What's more, because they're held in place by a barbed plastic tip – instead of just by their shoved-in bulk, as is the case with normal plugs – they're reportedly less likely to actually increase the size of holes as they're inserted.
Some of the material does end up sticking out of the tire after the repair, but that excess is said to quickly wear away, resulting in a permanent seal that can't be felt by the cyclist as it contacts the ground – even if used on road bikes.
The Dart tool tips the scales at 15 grams, with its flip-around double-ended head loaded with two darts. It's available now for US$25, with dart refill 5-packs selling for $20. You can see it in use, in the video below.
According to newatlas.