Serta's Tranquility Eco Firm 2-Stage Premium Innerspring Crib and Toddler Mattress by Delta Children achieves a strong, stable and safe sleep surface that's made especially for your growing baby. Built with 120 heavy-duty innerspring coils for long-lasting firmness, air vents to keep it fresh, plus a durable two-sided design, it will withstand years of use. Just flip it as your child grows; it's hardworking on both sides. One side provides the ideal firmness for infants while the other offers a layer of natural cotton for toddlers. Designed by the same brand that's been leading the way in mattress innovation and technology for more than 80 years, Serta's crib and toddler mattresses deliver the same quality craftsmanship and attention to detail as their adult mattresses. All Serta crib mattresses are GREENGUARD Gold Certified and meet the strictest standards offered by the GREENGUARD Environmental Institute, which recognizes products with low chemical emissions, contributing to improved indoor air quality.