Tannus Armour is a special insert that wraps around your tube providing up to 15mm of puncture protection in addition to other benefitsIn 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 - *except for fat tire sizes*The Tannus Armour sidewall helps stabilize your tires on corners and cushion the ride for more comfortUse 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 fit20x4.0-4.8Individual420gUPC/EAN/GTIN: 193751005629