There are more expensive mattress options but this is perfect for the price. I had twins sharing a crib on this mattress and it has held up well. It has shown no sign of breaking down and our sheets fit perfectly!
View Sealy Baby Posturepedic Crib Mattress
I found this on BabyAge.com. That site rocks b/c it lines all of the items up by price instead of whoever is bidding the highest.
View Sealy Perfect Rest Crib Mattress
The mattress was everything it advertised itself as. I am in my third trimester and EASILY lifted the box it was shipped in to bring it inside. When we unwrapped it, there were no nasty fumes coming from it - we didn't have to air it out at all! It fits perfectly in our Graco Somerset Convertible Crib, without any bowing or scrunching up in the corners. It is plenty firm, and sprang back immediately when my husband tested his weight briefly on it. I would definitely make this purchase again!
View Sealy Soybean Plush Foam Crib Mattress