This is the Sea & Sea YS-D3 Lighnting Underwater Scuba Diving Strobe Light Features: Maximum Guide Number 33 Newly developed aspherical troidal lens on the flash tubes provides even light dispersion, no hotspots are produced Wide beam angle of 120Adeg or can even wider (150Adeg) with the optional diffuser Two-stage signal - Visual and Audible notification that the strobe is ready to fire Auto power off when the strobe is left turned on for a long time Newly designed circuitry and light-emitting unit produces powerful guide number of 33. In addition, a high precision aspherical optical troidal lens has been fitted over the two flash tubes to disperse an even light from the center to the edge. The strobe&';s beam angle will increase to 110Adeg by attaching the standard accessories Diffuser. When the optional Dome diffuser is attached, beam angle will increase to as wide as 150(TBD)