These are replacement drawer dividers for Akro Mill parts cabinets. The dividers also have the ridge on the edges to fit into the side slots and keep the drawers from expanding sideways. Pictures show original and 3D printed version.
Designed in OpenSCAD and printed on Prusa MK3.
NOTE: There are many more styles of dividers available in another of my listings please download and like from here: https://www.printables.com/model/383933-dividers-for-parts-organizer-drawer-storage-boxes
The author marked this model as their own original creation.