I spent a good deal of time looking for a mattress topper that is CertiPUR-US certified (it is crazy what chemicals and toxic fire retardants you find in some foam mattresses!).  So if you are looking for comfort as well as non-toxic and less environmentally destructive foam, then this is a great choice.  My daughter finds her bed more comfortable.  The topper is thick enough to significantly reduce the hardness of her bed, but thin enough that the sheets still fit on her deep-pocket mattress.