A rubber crumb base with a felt top layer offers a good combination of protection, durability and comfort. It also allows carpet with seaming to bed into the top felt. We use Super Velvet, a 12mm triple-layer product made from 80% pure wool fibres, bonded to a recycled rubber crumb base, providing the perfect combination underlay. Giving you the ultimate in Warmth, Luxury & Comfort, Performance and insulation. 3.00 togs.