100% cotton knit, zippered, fully enclosed, safety crib sheet. Portable play yard style crib sheets come with hemmed "pass through" holes for mattress hold down straps. All Portable Play Yard Style Cribs. 6 units per carton - color: Mint. Foundations® SafeFit™ Crib Sheets are designed to maximize safety through superior fitting. Recent studies show that a large number of child safety hazards are created by improper bedding on cribs. Appropriate fit and 100% cotton knit provides the ultimate in softness, durability, and safety.