If you’re a mountain biker, then you are no doubt aware of the increasing popularity of tubeless tires. For the uninitiated, these are tires that have no inner tubes, but that are instead partially filled with any one of various brands of slimy polymer goo. When the tire is punctured, some of the goo seeps out through the hole, and firms up upon contact with the air. They’re self-sealing tires, essentially. Because they don’t incorporate tubes, they also weigh somewhat less than a traditional tire/tube combo. On the downside, though, some brands are notoriously messy to install, and to keep airtight. They also don’t work with all types of rims. Well, if you like the self-sealing idea, but not the possible hassle of tubeless tires, there’s a product you might want to try: SLiME Smart Tubes - slime-filled inner tubes.