M
2021-10-05 14:48:58 UTCmalkalypse
This is a thimble. It looks like the spool of thread is not included.
A typical 3D printable thimble with dimples and flange. Available in three sizes: 14, 16 and 18 mm inner diameter. The thimbles in the image are 3D printed at 0.1 mm on a MakerBot Replicator FFF 3D printer.