I liked the idea of the gridfinity with the Harbor Freight Mini toolbox. I waited until there was a color I wanted, in this case, the purple one which was recently released. 

I created the top base and split it into 2 parts in order for it to fit in the top storage area of the US General mini toolbox. The top part will allow for 3u bin heights. 

Printed in PLA with Elegoo PLA+ white

each size is 136mm x 146mm x 5mm

*Disclaimer: I have heard from Harbor Freight employees that the toolboxes are manufactured in 2 locations, I only have the one from Cambodia so I was not able to test fit the one from the other location.