This is a 5x4x4 Gridfinity bin meant for a Rack Solutions brand 'World's Best Cage Nut Tool'.

Having used it, I can concur it is the Worlds best Cage Nut Tool.

The tool is seated deep enough that other bins can be stacked on top.

This Gridfinity bin was designed with the help of Tracefinity, but fitment was adjusted by hand.