Simple replacement for that knob that broke off or got lost on your shower diverter rod (push-pull or twist type). Has a 4.7mm hole inside — slightly smaller than the rod itself, so when you press it on, the plastic self-cuts its own thread and grips tight. No glue, no screws needed.

Material:

Print in PETG, ABS, ASA, or PA (nylon) - this part lives in a wet, hot environment, so you need something that can handle that without issues.

Don't use PLA - even if it prints fine and looks solid. PLA is brittle, and when you're pressing it onto the rod (especially with the thread-cutting resistance), there's a real chance it cracks or snaps. On top of that, hot shower water over time can soften PLA since its glass transition temp is low - it'll warp and lose its shape.

Print settings:

100% infill isn't necessary and honestly not the best approach for a small part like this with a thread-tapped hole. Better to bump up the wall/perimeter count instead — something like 5-6 perimeters instead of the usual 2-3. This gives a more solid, uniform structure around the hole where the threading happens, instead of relying on infill pattern which can be weaker right at the contact zone with the rod.