I can verify some of the things that robo has written. i was very underwhelmed with the XML T5's brighness. I thought that it was just because of the grossly misfocused beam, with the EOS Tactical's stock optic, but that may not be the case at all. I got out the XML T5 neutral 20mm star, hooked it up to a 4.2v power source, with a 51ohm resistor, to replicate the relatively low emitter current out of the EOS (I tested the 70-Lumen rebel EOS at 290ma, on high with fresh batteries), and with the emitter pointed toward the white ceiling, above the dining room table, I observed pretty much the same underwhelming brighness, this time with the modified McR-27 reflector. IMO, I too believe that the XML is not the emitter for the EOS. For an easy 30% increase in brightness, from 70-lumens to 91-lumens, you can swap the stock Rebel emitter for the neutral-tint LXML-PWN2. If you desire a wider beam than the stock emitter, I'd look into the Ledil brand of Optics. to see what's available for the emitter that you end up choosing. Optics are more efficient than reflectors, but I still favour reflectors myself, but I can't remember exactly why.