We live in a house with really good water pressure. I recently replaced our shower head with one that let far too much water through, to the point that it hurt to stand in the shower stream. Since our shower water valve does not control flow, I designed and installed this flow limiting washer to reduce the pressure to a reasonable level. It has a slot for a small screw driver and is threaded to screw into the back of the shower head. See the last picture showing how to install it into the shower head (the screw driver is sticking up in the picture) I printed mine in PLA. If you're concerned that your hot water will deform the part, you can print it in ABS, but at a typical water heater temp of 120F (48C) I don't think PLA will have any issues. I printed it with .1mm layers, 25% infill, 4 perimeters, and no support.