Designed to work in tandem with the Nook Pebble Mattress, the Pebble Organic Mattress Wrap employs a patented asymmetrical pebble design and cutting-edge innovations to maximize breathability. Air flows in valleys between pebbles creating an oxygen-rich crib environment while surface fibers with nano-technology prevent liquids from seeping into the mattress for easy-wipe clean up. It is stain, water and microbe-resistant so your baby has nights of clean, fresh breaths. Plus, the wrap is removable and machine washable for easy clean up. Specifications: Materials: Eucalyptus, Organic Cotton, Zinc, Polyester, Easy-Close Nylon Zipper Dimensions: 28" x 53" x 4" Note: Only for use with the Nook Pebble Mattress. Gift Wrap not available.