I don't know if they would fit a emperor 280 because I don't have one of those. I would also like to know myself.
However, Marineland makes aqua-tech, penguin, and emperor filters. I've noticed that a filter cartridge on an aqua-tech 20-40 will fit perfectly on a penguin 170 (because its the same cartridge sold in a different wrapper). I suppose the cartridge for aqua-tech 30-60 will fit the penguin 330 also. Seems to me that the aqua-tech filters are essentially penguin bio-wheels, minus the biowheel. Perhaps they might have a lower gph then the penguins filters, but they do seem to use the same parts.