The hooks are small and are designed to fit wire shelves with wires 6mm in diameter.  

The wires on my shelf vary slightly and for some of them I had to slightly scale the model in the slicer to make them fit more or less loose.

I designed these for a resin printer, but should probably work with FDM.

I recommend ABS like or similar resin with some strength if you intend to have it hold much weight.