Not for tools, purpose is for more lighter objects (bike cover, heated vest, gloves, hats, cool vest, maps, etc). I made these from 4" x 4" Plastic "fence post" purchased at Lowes. They also sell a 5" x 5" post. In retrospect, I should have just purchased a wider Pelican Topbox......oh well. These have not been tested.....yet. I will need all the storage space I can produce, come June (big trip)........without looking like the Beverly Hillbillies. Caps are also sold at Lowes for these posts. They may not appeal to everyone, but at least it gives you some other options for placing a square tool tube on your pannier racks down below....instead of round. Do the math: a 4"x4" square tube gives MANY MORE cubic inches of storage over a 4" round tube.....it will suprise you.