For the OEM GREY fuser sleeve, you can basically interchange them but you must alter the length to fit for the particular model you are replacing. However, for the LJ1000/1200/1220 you cannot interchange with other model because the diameter is a lot smaller.
On the "Compatible fuser film sleeve" we do not recommend interchanging them since the LJ5L/6L model has thinner materials than the LJ5P/6P and LJ5000, besides the different in length wise.