The 20º honeycomb grid for the OMNI18R OMNI™ 18-inch Reflector takes the reflector’s beam spread down to 20” and can be used directly on the reflector, with or without the reflector’s supplied diffusion sock in place. The grid snaps into the recessed outer lip of the reflector alone or on top of the diffusion sock. When used directly on the OMNI™ reflector, the grid and reflector are ideal for high output, Hollywood-style selective lighting with superior spill control and isolation. For close-in mood lighting, place the grid over the triple layer diffuser to further reduce the output and achieve high fall-off, high contrast low key lighting effects. The grid reduces the light output another 2/3f stop, allowing even closer placement at wide-open apertures without the “dark center” that is typical with beauty dishes.
http://www.paulcbuff.com/18hg20.php