Each of the PortABox range has been developed with the mobile photographers in mine, taking up very little space in the gadget bag, each PortABox is supplied with a zip up flat packed carry case. The High grade materials are identical to the Interfit Pro Range of Softboxes well known for providing a high quality light source. The window box is able to be used in a vertical position to enable 80% of the flashguns output to bounce of the ceiling, the remaining 20% of the light will create a nice soft catch light in the eye. To fit the PortAbox simply place it over the flashgun and wrap around the Velcro strap tighten as required. The STR153 Strobies PortAbox 22cm x 16cm ( 9" x 6") with window is designed for the Canon 580EX11 and Nikon SB900 flash units.