Simple standoffs for PCB etching. It keeps the lower side from the bottom, resulting in a more even etch. This is for 1.6mm PCBs. I would suggest printing more than four so that you can select the ones with the best fit and so you have some spare. Printing in a material that is chemically inert to your preferred etchant (which should be CuCl2 btw) is probably a good idea... I printed in PETg which is good with any etchant afaik. Due to the hollow design, it shouldn't add much buoyancy.

Dimensions: slot width: 1.7mm (for 1.6mm PCB + photoresist) distance from one end to PCB: 10mm on both sides (etchant bath should be at least 15mm deep)