This foam mattress topper was purchased to place on top of a very heavy mattress on a top bunk bed in order to make linen changing a little easier (because of low ceiling height).   The topper itself is fine but the elasticated cover provided with it is hopeless, far too tight fitting, with the result that the foam (only 1 inch thick) just crumples up.   The simple answer would have been a fitted (zipped) cover of the same material which would have allowed the topper to remain absolutely flat, a few bob extra perhaps but well worth it.  As it is this purchase has been a complete waste of money and I would not recommend to anyone.