INKUTEN TM Pre-filled Refillable Ink Cartridges for HP 950/950XL & HP 951/951XL (non-OEM) With 500ml ink bottle refill There are easy-refill hole and rubber plug on the top of each cartridge. It is very easy to remove the plug for ink refill and replace it back after refilled for the easy refilling. Compatible with Printers: Officejet Pro: 251dw, 276dw, 8100 - N811a, 8600, 8600 - N911a, 8600 Plus, 8600 Plus - N911g, 8600 Plus - N911n, 8600 Premium, 8600 Premium - N911n, 8610, 8620, 8630. The cartridge is transparent. It is easy to view how much ink left to prevent from lack of ink to cause air bubbles or how much ink filled in to avoid overfill for easy operation. The prefilled ink cartridges can be used as regular ink cartridges for an easy using. This cartridge can be easily refilled and reused again and again.