As others have noted, there appear to be 3 different types of HP 364XL black ink cartridge: CB321EE (800 pages); CN684EE (550 pages); CB322EE (photo ink). Armed with this knowledge from other useful Amazon reviews, I checked carefully that the item advertised and paid for was CB321EE. However, it was a CN684EE that arrived. After contacting the vendor they promptly refunded the £8.18 difference between what I had paid and the market value of the product I had actually received (gleaned from adverts for the lower capacity cartridge on Amazon). Clearly this ridiculous labelling system by HP is open to confusion and, potentially, mis-selling. I believe that HP should name the cartridges better to highlight the differences and that Amazon should insist on unambiguous advertising of which model is being sold via their website. Although disappointed to receive a lower capacity product than the one I ordered, I am heartened by the prompt response of the vendor in refunding the difference. The moral of the story: until HP improve their labelling, check carefully the precise product you are about to order; on receipt check that it is actually the one you ordered; if it isn't, contact the vendor immediately with a clear statement of what you want to happen, ie exchange, return or refund of difference. Finally, as others will have discovered before me, some apparently sexy and excellent value printers turn out to be very expensive if the ink doesn't last 2 minutes and cartridges are dear. I fear my HP Photosmart Plus falls into this category. Next time I replace my printer I will also compare prices of replacement ink before committing.