Picked this up recently and just tried it out. I have the Avast porthole and I find the 3 screw attachment a little finicky. Depending on your lens, you may not find a good spot to mount the porthole securely. I find it usually mounts crooked on my Canon macro lens. The BAO camear tube mounts on the camera using the tripod mount. Very secure and lets you adjust the tube further or closer depending on what you need. I found that I could extend the tube further from the body and allow me the working distance I need with that lens. I like it so far.