I have 2 of these. I purchased my first about 18 months ago. These are fantastic. The included magnets are strong enough for only one under even a decently sized Marine characters. I just have 2 under some of the bigger monsters and vehicles. They have held up perfectly. The only issue I have had is that I stepped on the door while it was down and cracked it but that is my fault. The box is completely fine. The trays are a great size and stick perfectly with the included magnets.
I can't recommend these enough