I looked at a lot of mattresses for the Orbelle Tian minicrib I purchased for a first grandchild (and read many reviews). To be clear, Orbelle says in the packaging not to use a mattress thicker than two inches, but there aren't a lot of two inch mattresses to choose from and I think that warning is just about how close to the top it will be if at the top placement. This mattress seems firm with some give and fits perfectly, with no gaps at all. And, I decided I would be pleased with this product. I did give consideration to the materials and current concern for natural products, but this seemed a good balance and I'll top with an organic cotton mattress pad and sheet. The reason for four stars is that I can't know more until it's been used enough!