Curasept Proxi T20 Soft Blue Interdental Brush 5 PCCurasept Proxi Treatment series interdental brushes in the T20 size. This is the ISO size 6 and has a core diameter of 2. 0mm. We classify the T20 as "Soft" and is ideal for sensitive areas. The Treatment series of interdental brushes is recommended for larger interdental spaces resulting from gum problems, dental malposition or dental treatments such as bridges or implants.