Micro needle Screw Cartridge Replacement For dr pen Derma Pen Micro-needling Pen 12 pin / 36 pin / nano Tattoo NeedlesDESCRIPTIO Micro needle Screw Cartridge Replacement For dr pen Derma Pen Micro needling Pen 12 pin 36 pin nano Tattoo Needles About Needle Cartridge Derma pen needle cartridge uses a knead rod inlayed with numbers of needles, combining with functional nutrition liquid, regularly rolling in the places which needed to cure. It can puncture more than 300,000 micro vessels on the epidermis within five minutes, forming an efficient nutrient delivery system