The world"s easiest crib sheet. Place the mattress in the zipper base, lay our flat mattress pad on the mattress and zip on the zipper sheet. When the zipper sheet is soiled, just unzip it no need to remove bumpers and zip on a clean one. Fits mattresses 52" by 27" and 4.5" to 7" thick standard crib and toddler bed mattresses. Covered zipper never touches baby. 200 thread count. 100% cotton sheet that"s soft and c ounce y for baby. The innovative two piece QuickZip Crib Sheet Set is designed to be simple, safe and stylish. The top zips off the base for easy changing. No more mattress wrestling or constant tying and untying of bumper ribbons. Unlike loose fitting sheets that can cause an entanglement danger to your baby, QuickZip fits snugly around your mattress. And since we preshrink all our fabrics, our sheets fit wash after wash. The starter set includes one zipper base and one zipper sheet. Most customers buy an additional zipper sheet for convenience, as well as our soft, waterproof mattress pad for comfort and protection. Buy a set for you, one for the babysitter and one for grandma. Hands down, QuickZip sheets are the best baby shower gift for any parent.