watch this video. the sig 150 w fire button auto fires if you slide your finger up or down as you let go of the button. CRAZY !!! this sucks because i was about to pull the trigger on this mod, now i will go with the 100w+. i was having a hard time deciding on which one to get. i hate the curvy lines on the plus and the 150w looks sweet. the extra 50 watts doesnt matter to me, so i got to go with the better performer which is the 100w+.