part of an effort to help out my crew team by printing replacement parts for our boat. designed after spacers for Vespoli eights 3mm and 6mm thickness inside diameter set to 13.1mm recommended to print with ->ABS because of flexibility. however if you love the environment ad you lose a lot of these in the water then you should go PLA because its biodegradable apparently. ->.1mm /.2mm layer height -> 4+ vertical walls ->little to no infill (helps with flexibility) -> little to no top/bottom walls optional (helps with flexibility)