No. Fuji 39mm and the X100 filter size are not the same job.

I'm Leo Liang. I run XT Filters. The mail that lands here keeps mixing two Fujifilm setups that only share a compact look: pancake XF lenses that take a native 39mm ring, and the fixed-lens X100 series that only accepts screw-in glass after an adapter — and that adapter ends at 49mm. Wrong diameter does not "almost" fit. It will not thread on.

XF 27mm-class: native 39mm

If you shoot interchangeable XF glass in the pancake class — Fujinon XF 27mm f/2.8 R WR is the usual example — the filter thread on the lens barrel is 39mm. That number is stamped on the front ring or printed in the lens specs. You screw a 39mm filter straight onto the lens. No adapter. No trim-ring dance.

That is the lane where 39mm CPL and 39mm protection belong. For a light polarizer in that size, start with XT003 CPL ($39.99–$69.99 across 39–82mm). Check the 39mm cut before you order — black 39mm has been out of stock on our side lately. For a dedicated black-frame protector cut for Fuji 39mm mouths, XT996 PRO carries a Fuji 39mm cut ($64.99–$179.99 by diameter). Buy the Fuji 39mm listing, not a generic "small" ring and hope.

X100: adapter first, then 49mm

The X100, X100V, and X100VI do not ship with a usable filter thread on the lens. You remove the cosmetic front ring, mount a dedicated adapter, and only then do you have a working mouth. That mouth is 49mm.

I already walked the trim-ring and focus-travel details in a separate note on why the X100 thread is 49mm. This piece is only the size split: after the adapter is on, shop 49mm. A 39mm ring will not catch. A 40.5mm ring will not catch. Stepping rings that pretend to shrink an X100 down to 39mm are the wrong repair for a wrong purchase.

Once you are on 49mm, the same catalog lines apply at that diameter: XT003 CPL or XT001 PRO CPL for reflections, XT996 PRO in its 49mm cut for protection, XT888 Bottom 1/4 ($49.99–$119.99) if you want mild night bloom. Pick the 49mm variant. The 39mm Fuji cut on the same product page is for the pancake XF lens, not for the adapted X100.

What not to buy

Do not buy 39mm because a forum post said "Fuji compact is 39." That shorthand usually means XF pancakes, not the X100.

Do not buy 40.5mm as a compromise between 39 and 49. Neither camera path uses it as the native working size.

Do not order one 39mm kit and expect it to cover both a 27mm XF and an X100 in the same bag. You need two diameters if you own both setups.

My own daily camera is not Fuji — GH7 with the 12–40 PRO II since March 2025 — so I am not writing this from an X100 walk. The thread numbers above are the physical mounts we cut glass for. If your lens name is unclear on the product page, email me the exact Fujinon or X100 model before you click buy. I would rather answer one message than reverse a ring that never seated.

27mm class: 39mm. X100 after the adapter: 49mm. Keep those two numbers on separate sticky notes.

— Leo Liang