The Interfit SGM200 Flex Mount is for the Canon 430EX and Sony HVL-F32X on-camera flash units. The Flex Mount is an integral part of the Strobies series of flash light shapers. There are several light shapers that attach to the Flex Mount. A Snoot, Barndoor Set, Softbox, Honeycomb Grids, and Bounce Cards are available separately.
The Flex Mount is correctly fitted when your flash cannot be pushed any further inside it and is flush with the central hole.
