The Classic Plus is a 5" deep, single firmness, all foam mattress with our hallmark ultrasonically welded seams. Made with CertiPUR-US® and GREENGUARD® Children and Schools certified foam. The Classic Plus is engineered to withstand wear and provide an even ergonomic support for the full span of your baby's crib mattress use. The Classic Plus offers BabySafe side seams, which are welded with ultra-sonic sound waves to keep wetness out, allowing the inside of the mattress to stay clean. BabySafe seams are dropped to the sides of the mattress creating a seamless waterproof edge with no decorative cording or holes on the surface. This eliminates entry points for allergens, bed bugs and fluid leakage. The Classic Plus offers square corners and edges to fit tightly into the crib, with no rounded corners or surface designs to trap dirt or dust mites. The rectangular shape of the mattress, the same shape as the crib, holds sheets tight to keep baby safe. The Classic Plus' medical grade,stretch knit mattress cover is compliant with all current safety standards. Its lightweight and pliable nature enables the baby's body to conform to the surface while allowing the inner construction to provide comfort and ergonomic support for which it was designed. The cover is vinyl, PVC, lead and phthalates free. It cleans easily with a damp sponge and won't retain unpleasant odors or stains.