Just got my Cactus V4 Flash Triggers from Gadget Infinity and so far they seem pretty good. Just a note to anybody who has a Sigma EF 500 DG Super, make sure you set the flash to Slave mode (pictured above) this stops the flash from switching itself to standby mode and will allow the flash to fire using the standard centre pin (required for the V4 Triggers) rather than the proprietary Canon pins.