M54 Male to M48 Male Adapter

The 0.75mm pitch threads on both ends threaded smoothly onto my reducer and filter drawer, no cross-threading at all. This slim 2mm adapter saved me from having to rearrange my whole optical train.

Finally a spacer that doesn't fight me—the 2mm thickness is exactly what I needed for my camera's backfocus, and the threads are clean enough to seat without any wobble. It's thin, but the 0.75mm pitch holds tight once snugged down.

This 2mm spacer screwed on perfectly between my flattener and camera, and the threads are clean enough that it didn't introduce any tilt. It's thin enough to keep my backfocus math simple, and the M48 female thread on the M54 side gives me a solid grip for swapping filters.