The BUG-A-BEAM Adaptor is the part that makes the mating of a Source-4 and our Bug-Light 400 or 800 not only possible but quick and easy. The 400 (or 800) MSR/HMI lamp offers many advantages in this particular application, its 6 mm arc gap is punctual enough and very well suited for such optical design. The 4 to 1 efficiency ratio of HMI versus Tungsten incandescent explains the two full stops gain.