Its a liquid latex sealant that goes in your inner tubes - doesn't need special inner tubes with removeable valve cores, and doesn't add much weight apparently.
i've using this in my inner tubes for ages, works a treat. Haven't had to repair a puncture out on the trails for over 6 months. You have to swap out the inner tube occasionaly or repair the punctures and remove the thorns. You should save all your valve cores as well as they can gunk up and make pumping the tyres up quite an effort !
only ever tried kenda self sealing tubes.they were sh17e.now using schwalbe hardclimber puncture resistant tyres.hope theydont puncture cos they are barstools to fit.......snapped 6 tyre levers.
ok they do roll well on tarmac,hardpack,dry groud ect but they are bstards to fit.......bead is hard as hell.might get some metal tyre levers but have black rims(dont want to scrape them).not bad on corners in dry conditions.definately not a winter tyre.