You need these if you would like to dehydrate soups, whole meals for tramping or camping (e.g. Dahl, Bolognese sauce (see photo) etc.) or would like to make your own fruit leather. I have done all of the above and also used these trays for drying rice for tramping. It is too small to dehydrate with the other trays. I also made beef jerky with the solid trays. They need a light oiling so that the food doesn’t stick on them and are very easy to clean. With another dehydrator I had to cut baking paper to size for some of the above but these trays help and I don’t need the baking paper anymore. These trays have made it easier to dehydrate some otherwise tricky to dehydrate food. I like them and can recommend using them.