The filter thread size of Olympus M.Zuiko Digital ED 12-50mm f3.5-6.3 EZ is 52mm.
Below are links to the filters that we recommend you to consider for your Olympus ED 12-50mm f3.5-6.3 EZ:
Read our detailed Olympus M.Zuiko Digital ED 12-50mm f3.5-6.3 EZ Review