The Visual Echos FX6 Better Beamer Flash Extender will help to increase the reach of the flash, and increases the flash output by about 2 to 3 f/stops. It focuses and concentrates the output of the flash into a narrow beam via the Fresnel screen that gets positioned in front of the flash. This allows shooting at greater distances and shooting with smaller apertures.
The Better Beamer is designed to be used with lenses 300mm and longer. Its rugged injection-molded plastic side supports are attached to the flash head by a sturdy elastic "hook-and-loop" band. The rigid supports hold the Fresnel screen in place in both horizontal and vertical formats. Just weighs 2.5 oz.
The FX6 version is designed to fit the Nikon SB-5000 AF, SB-910 AF, SB-900 AF Speedlights and the Canon Speedlite 600EX II-RT, without any need for use of additional "shims."