Tannus Armour is a special insert that wraps around your tube providing up to 15mm of puncture protection in addition to other benefits. In the unlikely event you do get a flat tire you can still ride for a limited period of time with less risk of rim damage - *excludes fat tire sizes*. The Tannus Armour sidewall helps stabilize your tires on corners and cushion the ride for more comfort. Use of Tannus Armour requires use of a smaller tube see links tab on website or contact your local rep for details. *Minimum inner rim width needed to install the inserts is 19mm. *Smaller ends of the listed size range may need trimming of the sides to fit