CowboyStudio 3 in 1 Stacking Grid Light Modifier System for NIKON SB900 / SB910 Flash Speedlite One (1) 3 in 1 Stacking Grid Light modifier It is designed for NIKON SB900/SB910 The JJC Light Modifier was designed to produce 3 different size of light spread (Small, Medium and Large) when aligned and stacked two grids together, produce the smallest spots of light. Stack the small grid into the bezel to produce large size spots of light, for medium size spots of light just stack the larger size grid into the bezel.