This is a pair of 1.9" Dual Stage Closed Cell Foams for Rock Crawlers. Pro-Line's inner inserts are made from lightweight and waterproof blue closed cell foam while the outer is made from soft open cell foam. When combined they are perfectly sized for Pro-Line's 1.9" XL sized rock crawling tires. The soft outer foam provides maximum grip while maintaining a fully supported sidewall from the inner closed cell foam for maximum side-hilling performance. Dual Stage Closed Cell foams are extremely durable and will last through many rugged adventures.