I replaced an ignition key cylinder on an older Ford Explorer and gutted out all the old tumblers, so any new uncut key blank can turn the cylinder. If I have one working key I often will remove the key cylinder and slip in the key cylinder without the tumblers to program the uncut key blanks before wasting any time having them cut , that way I can return the new uncut key blanks for a refund or exchange in the event they can't be programmed.