These trays are designed to fit the Commercial Chef CCD100W6/Westinghouse WFD100W food dehydrator and allow drying of items too small for the stock tray openings - I use them to dry out loose desiccant from my filament storage boxes.
Four size provided:
Recommended to print with zero top/bottom layers, and Rectilinear infill of 25%. This results in openings that are small enough to keep desiccant from falling out, while still allowing air through.
The author hasn't provided the model origin yet.