I have two of these trays. They are great. I ended up cutting up pieces of plastic..may it is rubber liner. The sort you can buy in Walmart in a waffle weave. I also have it on my drafting table so things don't slide off. It allows the pastel dust to go through the liner and the wire onto the tray. I am not sure why I did this, perhaps fussing, however it provides a softer surface for my pastels.
I also got some foamcore and cut out a lid to cover the top of each tray. A nice insert over the top of each tray which still allow you to stack them. It protects the pastels when not in use. I can also put books and other things on the top of the trays without damaging the pastels. The trays are a good deal. Lots of room to sort your pastels and add more
I am sure you will love your trays!