"Camera & flash combination other than Canon & Nikon : To establish which model is best suited for a particular combination the distance between optical axis and the middle of the flash units reflector needs to be measured. This measurement will allow the user to find the best match with a RAY FLASH"

they're fairly light on power and heavy on recycle compared to top end brand stuff
makes them real nice hair/separation lights but in a rayflash you lose a lot of power and really need it
Calumet used to stock the Rayflash, don't know if they still do.
i bought the Coco and thats pretty good though its clear that its cheaper, as flash says, avoid O flash.
not sure if there was a copyright issue, i picked mine up just in the last couple of weeks - the chinese manufacturers who dont follow copyright laws never seem too bothered about anything. Im waiting for my stigma to come back from rechipping before giving it a proper go but initial tests of the dogs seem to show pretty good even lighting from it