Thanks for your question. A dermaroller going to 3mm depth is not something someone should be using at home. Dermarollers in general for this condition are not the treatment of choice. There is a big difference between a dermaroller and a medical microneedling device. As the dermaroller "rolls" it both pierces and drags the skin, creating uneven cuts (think like the edge of a saw)- and the deeper the depth of the needles the more pronounced this will be. A medical microneedling device has the needles moving up and down perpendicular to the skin and at such a speed that by the time the handpiece is moving the needle has retracted (think movement like a sewing machine up and down at high speed, not dragging through skin). Then there is the question of the quality of the needles, how quickly they will dull, and the fact that most of these dermarollers cannot be sterilized. You are asking for trouble. Medical microneedling can work nicely on stretch marks, especially when combined with PRP (platelet rich plasma). best, Lisa Vuich, MD