2.2" Dual Stage Closed Cell Inner/Soft Outer Foam Inserts (2) for Pro-Line XL Rock Crawling Tires This is 2 pair (4pc) of 2.2" 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 2.2" 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.