The falcon eyes fer-ob9 octabox has a diameter of 90 cm and can be mounted on your studio flash unit with the included speed ring. the studio flash head sits deep in the octabox, which ensures minimal loss of light and provides an even spread of soft lighting. The fer-ob9 is supplied with a standard falcon eyes speed ring. this speed ring is compatible with all falcon eyes studio flash units except for the falcon eyes ss series. by using an additional speed ring adapter, the fer-ob9 is compatible with bowens, broncolor, elichrom, hensel, multiblitz and linkstar studio flash units. to view these speed ring adapter rings, please see the optional accessories tab below. *the following link provides an explanation of how to set up your octabox: how to set up an octabox These softboxes are not suitable for halogen lamps, (such as the falcon eyes qlt-1000), due to the high heat generation of these lamps. the soft boxes from the sbq series are suitable for such types of lamps.