Arrow nock. I've printed it at a 0.1mm layers and dropped speed to 10mm/s with 35% fill will test it on a low powered bow 1st and then maybe my 20# recurve.
More Archery posts in my group http://www.thingiverse.com/groups/3d-toys

If you want to see more and how I create prints and 3D designs like this check out my YouTube channel. https://www.youtube.com/channel/UCSHUc93NXGwBacoIDDqPU2w