Those are great plastic shelf units. When I was putting the ones I have in my garage together, I ran a three inch screw through the shelf, to attach the unit to the wall studs so they won’t tip over easily. Makes then that much more stable when loaded down.
Good idea. I set-up 10 of them for Dad in his basement, and we had to both shim-up the front legs and secure them to the wall: his concrete floor wasn’t perfectly flat. I checked my Condo’s basement floor w a level, and it’s perfect, but since it’s a CB wall, I’d have to use lag-bolts into the block. So I put the heavier weight on the lower 2nd & 3rd shelves, just so they wouldn’t get top-heavy. But I might consider some lag-bolting, just for an extra measure of stability.