For flat chests, it's recommended to choose either the 5cm or 6cm models (the 5CM model has a thickness of about 3.5CM in the middle, while the 6CM model has a thickness of about 4.5CM)
For small busts, we recommend the 2.5cm model (2.5CM model has a thickness of about 2.5CM in the middle). The 5D thickened silicone model has a cup height of 5CM and a thickness of about 3CM in the middle