New 2-way zipper for easier diaper changes. For added comfort, there's a flap of fabric inside the collar to cover the zipper and protect the baby's sensitive skin. MEDIUM-WEIGHT INTERLOCK (Interlock is a knitting technique that sandwiches 2 layers of jersey and results in a smooth surface on both sides, inside and out.) 100% Pima Cotton With the longest cotton staple in the world, Pima cotton is luxuriously soft, washes great, never pills, hardly fades, and lasts practically forever.