Sprinkler Head Donuts - Full Round and 1/2 Round

Print these out of PETG which is much better than PLA for durability and UV resistance, These work great if you follow these instructions; buy a bag of portland cement only (NOT CONCRETE, nothing with aggregate in it!). Masonry cement will be the same thing. Buy another bag of high quality SAND. Mix a small batch of the two together, 1 part, by volume cement, of cement, and 3 parts, by volume, sand. While mixing, add just enough water to make a batter a little thicker than pancake batter, barely pour-able. Turn the donut over, and fill it all the way to the top with the fresh mortar mix. Let cure, at least 24 hours, three or more days would be better to achieve maximum strength. The finished donut will be MUCH heavier and MUCH stronger, and will NEVER get sucked up by ANY lawnmower and they hold up to being driven over by big lawn crew-type mowers!. I've been 3D printing plastic sprinkler donuts similar to these for years, and this process works PERFECTLY!!! As noted in the file names, the full round donut is my 7th major design iteration and the half round is my 4th iteration. We have OVER 100 sprinkler donuts in our yard, so I was able to observe their durability and make design improvements as I populated the yard with donuts, I have an older Gen 1 design on Thingaverse which you should disregard, The number plates should be revised to reflect your needs. I used Autocad Fusion 360 which is free to private individuals. I use these 1/4"-20 x 2" SS bolts to hold the number plates, concrete, and 3D printed 'shells' all together: https://www.amazon.com/dp/B0F5MF7HYD?ref_=ppx_hzod_title_dt_b_fed_asin_title_0_0&th=1