Application: Just replace the needle. Needle length is adjustable to different sizes depend on the areas . It is more convenient to treat narrow area such as nose, around eye or mouth. Features: Item: Derma Pen M8 Needles Needle Type:11/16/24/36/42/Round Nano/5D/ Quantity of needles: 10/ 20 Pieces needles, not including box and machine It is an eletronic automated micro needle,with guides that adjusts needles length. It is hygienic,convenient,and safe. Dr pen M8 features exclusive cartridge with arc edge which fit the skin better and work more smoothly on the skin.These replacement cartridge needles only fit for Dr pen M8 Advantage: 1.Minimised epidermal damage 2. Less pain and erythema as high speed with vertical direction 3.More easy to operate at the small or curved areas 4.Disposable needles 5. More quickly and efficient than manual Micro-needle 6. The treatment effect is obvious 7. Short healing time. 8. No permanent damage or injury. 9. No bruising, infection, discoloration or other complications. 10. Extremely high absorption of any active ingredients. 11. Almost all skin types can be treated. 12. Thickens the dermis without damaging or removing epidermis.