I just needed a holder for my sunglasses that was magnetic and big enough so the sunglusses would not be in contact with any other surfaces.

The 15x5 mm magnets are incredibly strong.

I just added some painters tape to avoid damaging the metallic surface.

The holes are 15.2 mm wide and 5.1 mm deep. I used some instant glue to fix the magnets.

Onshape link in case you want to modify it: https://cad.onshape.com/documents/ebdd9c6b445ce2f5b3ff4701/w/39525df4dfcde24b38a9fee3/e/4af82b8a55d21ab40c9463b4?renderMode=0&uiState=66ac770f841560686c605472