The bulb on my old Flowtron Mosquito zapper went out, so I purchased this new one not knowing they also just sell the bulb for my old model, I believe.  Amazon doesn't say what model the Dark UV CFL is for so I have no way of knowing.  I didn't hear as many zapping sounds with this Flowtron as I did with my old Flowtron.  However, when I checked the zapper after a week, I did notice a lot of dead bugs, mosquitos, inside the octenol lures.  The light blue color UV CFL does not seem to be as effective as the old dark purple color UV CFL bulb.  I'm not sure if they are compatible with both models, I do not believe they are.  Overall, it works, but as good as the older model, eehh.