First I must say that I have been extremely pleased with my Sigma 105 since I purchased it last summer and can't wait for spring to get here...however, since day one there was always something I didnt like about and that was that you couldn't reverse the hood on it when storing it...well, I don't know how many people know this but the open end of the sigma hood is 77mm...I know this because I purchased a 100-400L back in october and that has a 77mm front element...I hated how the front lens cap was hard to take off when I had the hood on the 100-400L so I bought a 77mm pinch cap to use on the 100-400L...now dont ask me why but for some reason I looked at the Sigma hood and the next thing I knew the 100-400L's cap was attached to the Sigma hood and fit like a glove...so there it is, my tip is that a 77mm lens cap fits on the Sigma 105mm Hood if you want to leave it on since it can't be reversed.
I am sure this post is probably going to be useless for most but just in case it might help someone I figured what the hey.
