A sealing system and sealing composition are provided for inflatable articles containing air under pressure. The sealing composition includes particles or particulates of three-dimensional shapes having sharp corners thereon which tend to dig into the article around the opening and wedge themselves therein. The sealing composition also includes fibers, at least some of which are fibrillated. The fibers tend to wrap around the particles and further plug the leak opening. The particles and the fibers are in a liquid carrier which also tends to form a bond of the particles and fibers in the leak opening. The particles in the composition have dimensions covering a particular range of sizes for different articles, the larger dimension being useful in larger dimension articles, such as large tires for construction machines, and the smaller dimension being useful in smaller articles such as footballs and basketballs, for example.