this is a 510 drip tip I made in blender, i called it a tophat, because it sorta looks like one. read the instructions. rotate 90 degrees so it is sitting on its bottom, print with raft and supports on blue painters tape. I used fine/high quality, and 100% fill since it is such a small and delicate piece. an O-ring should fit nicely, and it should be snug with the O-ring if you got all the support material cleaned out of the groove. I used a tiny flat file to get all of it out.