Quantity:  10pcs. Cartridge: 11 pin / 16 pin / 36 pin /24pin/ 42 pin/ nano Needles... (Only Suit For M8). Application: Just replace the needle. Needle length is adjustable to different sizes depend on the areas and purposes of the treatment. It is more convenient to treat narrow area such as nose, around eye or mouth. Features: It is an eletronic automated micro needle,with guides that adjusts needles length. It is hygienic,convenient,and safe.The perpendicular movement of the needle tip enables treatment of narrow areas, and lessen the pain. Note: If you need others Pen, please contact us. Thanks !