Pixco M42-Fuji X "Speed Booster"

Not a real "Speed Booster", because that's a Metabones trademark, but same idea: this adapter to mount M42 lenses on a Fuji X camera includes a focal reducer to eliminate the Fuji sensor's 1.5x crop. Extra benefit: you gain a bit of light. Downside: corners can get soft wide open. It's not perfect, but it's a pretty decent solution if you want to pretend you have a full-frame camera.