A few weeks ago I was reading a thread that Alex Mustard started initially talking about a problem he had with his aperture sticking on his Tokina 10-17 lens. The thread devolved a bit into problems people are having with the lens coming apart by removing the rubber ring on the lens in order to get the Nauticam zoom gear to fit. They have resorted to using different kinds of tape to hold the lens together. See: http://wetpixel.com/forums/index.php?showtopic=41838
I had mentioned in that thread that I wondered why I wasn't able to get my zoom gear to fit. For some reason there were no instructions that came with the gear and no one at the store I purchased it from could figure out why it wouldn't fit on my lens. I would never have thought to remove the rubber ring on the lens.
Anyway, by chance I decided to try another zoom gear I had purchased for my Tamron 10-24 lens and that worked so I just sent the other zoom gear back. My question for you is why do people buy the zoom gear that requires you to take apart your lens in order to get it to fit? Nauticam sells another zoom gear called "Nauticam Gear for Sigma AF 10-20mm f/4-5.6 EX DC HSM Canon", part number SKU-19535 that fits the lens without requiring you to remove anything on the lens. I used this configuration for a week in the Red Sea and didn't have any problems. I'm wondering if there is something that I don't know and I'll discover a problem on a future dive or are people just not aware that this zoom gear fits the Tokina?