Dr. Pen uses sterile, individually-sealed, disposable needle cartridges for optimal safety and comfort.<br />The adjustable dial allows treatment that adapts to individual client’s needs. (Notice that the maximum depth depends on your cartridge's type)<br />Dr. Pen is more economical than derma roller, you just need to recharge the pen and replace cartridges after every use. The battery of Dr. Pen Ultima M5 is built-in. Both wired and wireless can be worked. ">