This is a Panasonic-made lens that comes with an Olympus/Panasonic Micro 4:3 mount. The filter size for this lens is 77 mm, so make sure the filters will fit.
From Photospecialist
Panasonic Leica Elmarit 200mm F2.8 Power IOS
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Panasonic LEICA DG ELMARIT 200mm F2.8 POWER O.I.S. with 1.4x Converter
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Panasonic 200mm F2.8 LEICA DG ELMARIT POWER O.I.S Lens