The filter thread size of Olympus M.Zuiko Digital ED 100-400mm F5.0-6.3 IS is 72mm.
Below are links to the filters that we recommend you to consider for your Olympus ED 100-400mm F5.0-6.3 IS:
Read our detailed Olympus M.Zuiko Digital ED 100-400mm F5.0-6.3 IS Review