Add Another 20mm of Cushioning Beneath Your Mellow MatA purpose-sized memory foam underlay with non-slip fabric on both sides.The Mellow Mat Underlay sits beneath a compatible Mellow Mat to add another 20mm of cushioning. It is intentionally made slightly smaller than the mat so the Mellow Mat edges can still sit down towards the floor.Five underlay sizesChoose Small 0.76 x 1.26m, Medium 1.26 x 1.76m, Large 1.76 x 2.76m, Huge 1.76 x 3.76m or Square 1.76 x 1.76m.Non-slip fabric top and bottomThe custom surface is designed to help the underlay stay positioned beneath the mat on suitable floors.Allow it to expandThe underlay arrives compressed. Allow approximately 14 to 21 days to expand naturally, or use steam carefully. If using an iron for steam, keep a tea towel between the iron and underlay.