My crib measures 53 inches long. The sign at the store said this mattress was 52.5" long and the tag reads finished size of 51.75". When I put it in the crib, I could fit almost 4 fingers between the mattress and the crib. When I measured the mattress with a tape measure, it only measured 50". Make sure you take a tape measure when choosing a mattress. By the way, Babies r Us was very helpful in the return of the mattress.
With a baby due in two months' time and a toddler moving to a new toddler bed, we went to Babies R Us to buy a new crib mattress. With so many choices, we finally just commandeered the floor near the mattress display and set one of each mattress out, then had our toddler try each one (both in a snuggled sleep pose and as an active kid jumping on the mattresses). The Sealys we quickly discounted -- they compressed too much with our son's weight on them, even when he wasn't jumping. The Pediatric mattress was the opposite -- hard as a brick. The Beautyrest was "scratchy" according to our toddler. It came down to the two Serta mattresses. To be honest, we could not tell the difference between the Perfect Night and the Perfect Sleeper, other than the price. The dimensions were exactly the same (we stacked them to compare), they were firm without being hard, and our toddler liked the stars and clouds on the Sleeper... which is $50 less. The Sleeper now sits in the crib, fitting perfectly (so perfectly I broke a nail making up the bed). A highly recommended mattress.
back when I brought this I couldnt find anyone to ship it. It was a gift for my god-daughter she was so happy to get it! Although whoever you used to deliver it left it right outside the apartment door