I think you mean height. The longest dimension is length which coolcole pointed out. Width and height are standardized. There's half height which are slim cases and there's full height which is most desktops like yours. For a tower, height actually goes sideways, from the pcie slot out the side of the case. Width is single slot, dual slot, and the rare triple slot. Most cards are dual slot. So only length changes for most mid to top end cards. This is different than what you think it would be because it just carries over from the older days when pcs were laid on the big side, not standing up like towers.