See the instructions here
(produces a narrower beam than our 1/4 Speed Grid) Our 1/8 Speed Grid has a 1/8" honeycomb cell size to narrow the beam of light from your portable flash unit, producing a small circle of light on your subject. Fits most any shoe mount and most handle mount portable strobes, including Canon 420 though 580 and Nikon SB24 though SB800. Attaches quickly and easily to our Speed Strap mounting system (not included, sold separately). Usable honeycomb area is 3.5" x 2.25" (appr. 89mm x 58mm)- simply measure the front outside dimensions of your flash lens to assure fit. Rugged ABS/polycarbonate construction. Patent pending design.