Thanks for your reply. I read one other review online and person said that photoflex speedring did not fit properly onto Einstein head. I want to buy the light but now I am not sure. I have 3 photoflex boxes already and don't want to invest into new ones. The plan was to use the larger box mentioned for location shots outside. After using the light I really liked its performance. Do clips on box seat all the way on speedring? Not very good if you have client see you equipment fail.