L4 Lumamax lights have a KL4 5 Watt LED head on them. That is what makes them an L4. The letter "K" was an arbitrary addition to the name to designate it as being the head alone, without any body. You can buy the KL4 5 Watt LED head by itself to use on an E2e to make it an L4 (functionally). It just won't have the "L4 Lumamax" name on the light. To my knowledge, the KL4 heads separately or on an L4 are the same(save for the "Luxeon Lottery" and any colour differences in the HA coating).