The Nikon R1 Speedlight System (A.K.A. "Macro Kit B") is designed for Nikon DSLRs that feature both, the "Commander"mode, & include a built-in flash. It is fully compatible with the Nikon Creative Lighting System, & Advanced Wireless Lighting System, when used with compatible cameras & flashes. The system includes a SX-1 Attachment Ring, which is made to attach to the lens filter threads, via an included adapter ring, & two SBR-R200 Wireless Macro Flash Heads. The Attachment Ring is designed to accept up to eight SB-R200s, & can be attached to a tripod for remote lighting. The R1 Speedlight System has a Guide Number of 66 ft., at 24mm, with both heads. This system allows you to experience close-up lighting control, with flexability, & versatile options.