Sigma Flash Macro Ring EM-140 DG for Canon SLR Cameras

I'm relatively new to photography. I have lots more equipment and software than knowledge and experience. I bought the 140DG based on one owner review and the price (compared to Canon's). I'm glad I did. This light works (as far as I can tell) exactly like Canon's Mr-14EX. Sigma won't say it outright, but the 140DG controls and fires my Canon 580EXII and 430EX without any problems at all; and indoors, at least, the slave flashes can be placed anywhere, even behind the camera. Not only is the price better than Canon's, but a fantastic advantage of the 140DG is that, with available adapters, it will go on the nose of my 24-105/77mm-filter lens. The 14EX only goes up to a 55mm filter-size lens; plus, the Canon light needs to go into groves at the front of their Macro lenses. The Sigma has threaded adapters that screw in like a filter, and then the Ringlight catches grooves in the adapter.
I can't say much about the relative build quality compared to Canon, but I do know tools, and there doesn't seem anything wrong with the build quality of the Sigma.
All in all, I recommend it highly.
Buy Sigma Flash Macro Ring EM-140 DG for Canon SLR Cameras!