I am looking for a mudguard to buy but cannot figure out sizing etc. I have a Fuji sportif 2.5 road bike. I am worried the one I would get wouldn't fit through the brake system or would be too wide. Do you have any advice?
SKS Raceblades will probably fit: https://www.sks-germany.com/en/products/raceblade-long-black/
They are specifically designed to mount around road bike rim brakes like you have.
Mounting them may require a bit of tool work, mudguards are rarely "plug and play."