We do NOT recommend using BOOMBA inserts under thin, unstructured or loose tops. In thin tops, the outline of the inserts may show through.
We recommend using BOOMBA inserts in tight tops with structure. A good guideline to know if the material of your top is thick enough to hide the outline of BOOMBA inserts, is by checking if the material is thick enough to hide the shape of your nipples.
You can see examples of some outfits here.