Made from Super comfy stretch corduroy so nothing holds them back. Front lined for warmth and a little extra strength when crawling. Outside:97% cotton, 3% elastane stretch corduroy. Linings: 100% cotton. Adjustable elastic waist - buttonhole elastic. 6-12m size has poppers on inside leg. 12-18m does not. Please note this is the slim fit style and may not fit babies with average to large waists. The dungarees and the denim baby jeans are a more generous cut.