Sto-Fen Omni-Bounce for the Sigma EF-500ST & EF-500 Super Flashes. The Omni-Bounce creates a diffused bare bulb effect, giving even coverage across the entire frame, with lenses from 15mm to 200mm in the 35mm format (and equal in other formats as well). The Omni-Bounce is easy to use and goes onto and off the flash in seconds with custom fitting (except for UNI model) and no touch fastener. Designed for years of service without the bulk of some other diffusers, it is small enough to fit easily into a gadget bag or pocket.