Review on ⛑️ Waterproof Pack N Play Mattress Cover 27" X 39" - Fits Most Playards, Foldable Mattresses and Pack and Plays - Fitted, Comfortable and Soft Mini Crib Mattress Protector by Little One's by Eric Render

This mattress topper fits almost all travel cots with a few exceptions. One of the exceptions listed is that lumps can form on the 1-inch mattress that comes with Pack 'n Play. That's exactly what I wanted to avoid. I had another similar mattress pad that deformed my Graco Pack 'n Play mattress (see photos). The mattress topper manufacturer suggests buying a thicker mattress to avoid wrinkling, which I don't want to do for safety reasons (too thick or wrong size). I bought a brand new Pack 'n Play because I couldn't get a new mattress and I don't want to spoil it and this mattress pad would do just that if I didn't return it. I figured the solution was to use Graco stretch sheets which have no stretch and Graco makes a waterproof version too. Any bed sheet or mattress pad with elastic bands seems to cause 1 inch wide folding mattresses to stick together.