What you have here is a TTArtisan-made lens that sports a Fujifilm X mount. If you want to use a filter on the lens, then the filter size is 43 mm.
From Amazon
TTArtisan APS-C 25mm F2 Metal Bodied Lens Compatible with Fuji X Mount - Black
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TTArtisan APS-C 25mm F2 Lens
WEX Photo Video
TTArtisan 25mm f2 Lens for Fujifilm X - Black