Flex mounts are needed to attach Strobies products to your flash unit. Fitting a Flex Mount could not be simpler. The flex Mount is correctly fitted when the flash gun cannot be pushed any further inside the flex mount and is flush with the central hole of the Flex Mount. Color gels may be fitted inside the Flex for creative effects. You do not need to use any glue, rubber bands or Velcro on the Flex Mounts, they stay in place when properly installed. Front mounting clips on the mount allow quick attachment of Strobies products allowing you to change from a Beauty Dish to a Snoot in seconds. This Flex Mount is designed to fit Vivitar 285 HV flash units.