For those of you that use dermarollers with long nails.. how do you calculate how much milimeters are you penetrating?
For instance Somebody uses a 1.5mm if I remember correctly daily but he says he doesn't go deep.. so how deep can you know how you are going? seems random as f***.
Just buy the ones that have the correct depth and always press hard. I have a 1mm and a 0.25mm roller. The latter for absorption