Pop 'N Go 3.0 Mat & Mattress Cover Combo Waves - Designed to fit inside of your Pop N' Go Playpen! Simply twist the cap on this self-inflating Pop N' Go Playpen Mattress to add cushion and support to your little one's play space. A water and sand-resistant finish makes it perfect for indoors and outdoor adventures. Included is a super soft organic bamboo mattress cover that is removable and washable.