I have picked up 300mm f4l is and it didn't come with a tripod collar. Does anyone know of a knock off tripod collar or what lenses share the same collar. I asked this question before because I see replacement tripod collars for the 70-200's and the 300 f4l but not the is version. I was told that the 300 f4L and 300 f4L is should be the same but it's not. I ordered one and it does not fit I ordered the cheap opteka $25 collar so no big deal. I have been looking at images of lenses side by side and it looks like the 100-400 and 70-200 2.8 collar would be the same size. Any info would be greatly appreciated.