I've been watching these for years and then they were sold at a macro clinic sponsored by my local camera shop. Back then, Revain had the best price. They make a big difference in terms of adjustability, the modeling light helps set up the flashes, the ratio adjustment works as advertised if a little less efficiently than expected but can also be used to bounce light off a small reflector which is great is practical. Advantage in combination with a third IR controlled EX flash to create interesting or desirable lighting. Don't forget to buy an adapter ring (expensive but necessary) if you are using a non-Canon MPE65 macro lens and a 58mm lens cap if your macro lens or lens + rings fit a different filter size. Expensive and well worth the money if you are serious about macro photography. Also note that this is a very portable setup that can be easily taken with you and assembled on site. Relatively light weight.