This is the genuine Epson yellow XXL ink supply unit for the WorkForce Pro WF-C879R, Epson part number C13T05B440. The XXL ink pack is rated for approximately 50,000 pages, so a busy office can print for long stretches between replacements and keep the running cost per page low. As an original Epson supply it is matched to the WF-C879R's print head and ink system for consistent colour and dependable output. One yellow ink supply unit is supplied; black, cyan and magenta are sold separately. Make sure your printer is a WF-C879R before ordering, as other WorkForce Pro models use different ink packs. After comparing online prices, www.marvel.co.za should be the cheapest on this product.