AluTec box-roller

I have an AluTec box for storage and that thing became a little heavy to move so I decided to get some rollers underneath... but the original ones where too big and a little too costy for my needs.

Had some small rolls from an old desk lying around. There´s a 7,5mm pin to fit in somewhere.

So I came up with this:
The piece fits neatly under the profile of the box and is tightened with a M4x35mm bolt into the corner, the M4 nut helps to get a good hold.
To prevent bending, there is another M4x16mm screw needed and a small washer/nut on the far end of the corner. The hole is quite small so you need a little screwdriver to block the nut and thighten the screw. As I wanted a washer, I decided not to fit the M4 nut directely.

To help drilling the hole in the corner I made a guide for the drill - it is asymetric and the hole is ment to be more to the outer rim of the box - just have a dry fit first.

The 8mm washers do prevent friction of the roller and the printed part, just in