I designed a quick and easy overflow stopper for standard UK bath overflows of 40mm diameter with hexagonal stem. I retained 2 of the upper most over flow holes so that it still works as intended and shouldn't flood your bathroom.

I am 6'3" and for me to submerged in the bath and be truly comfortable the bath would be so full that as soon as i lay down it would start to drain through the overflow, so i created this hoping it would at least slow down the flow but it ended up working amazing and even after a 45 minute bath the water is at the same level! I love it and it was the first thing i designed myself after getting a printer.

I printed using PLA which has been plenty for the heat of bath water (been using it over a month) but I guess PETG would be preferable.