Universal Standard for Tubeless (UST) tires are compatible with UST tubeless and standard rims. When used with UST tubeless rims, the tire and rim form an airtight chamber, allowing the tire to be inflated without a tube. When used with standard rims, a tubeless kit and sealant (sold separately) can be added to the rims to create an airtight seal. Both rim setups let you run lower tire pressure for optimum traction and control without fear of pinch flats. And, UST tires can be mounted and inflated with a tube on both UST tubeless and standard rims.