We ordered the mattress to Kidsmax playpen David. The mattress is a simple foam pad with about 5cm thickness. The foam is (really thin) coated with a thin coating of cotton, which fits pretty much. We have the part washed unfortunately with 60 ° C, while it has been run in a direction approximately 5-7 cm. The mattress can indeed still fairly smooth in the reference constraints, but the mattress fills the bottom of the Laufställchens no longer completely. On one side now missing 5-7 cm. Well, we had the part probably should not wash so hot, even if you should really assume that it does not shrink. Especially with young children you have probably wash more often.
So, in principle, a good product, but the coating is not hot washable. So I would also recommend a waterproof pad in the appropriate size and above a fitted sheet or a playmat.