The above is correct. Dell printers are usually re-badged Lexmark, but they have a slight modification on the print cartridges.This usually consists of a plastic lip, which prevents Lexmark and Dell cartridges being interchangeable, unless you know how.
I refill all my own Lexmark cartridges, as they are so expensive to purchase new.Lexmark compatibles of certain types, can be difficult to find for some models. Each refill costs about 60pence if you use the readily available InkTec or JR refill kits. If you intend to refill your own,remember the golden rule,do not let the empty cartridges stand empty to long, as this may make them unusable. Refill straight away.
For Lexmark or Dell compatibles at a reasonable price click here