UltraMAX XTS combines extra heavy duty tube (600% thicker than standard at tread area and at least 200% on side walls) with sealant to give you the best protection against punctures yet. UltraMAX XTS has been prefilled with tube sealant that prevents flats by instantly sealing punctures up to 6mm in diameter. The sealant is forced into the opening by internal air pressure and upon contact with the outer atmosphere, bonds to the tube creating an airtight plug of flexible fibres permanently sealing punctures