3D Print posted by Larry
These are replacement spool holders for the Ultimaker 2 and Ultimaker Go. The one for the UM2 is shorter than the one supplied to keep the spool better positioned with relation to the feeder.
The one for the UM go is a little longer to allow the use of standard 1 kg spools.
Both have a roller to reduce the turning friction (and squeeking) of the spool.