Hello, these are reels for a pick and place machine. I bought a PNP recently and had lots of SMD/SMT parts around that were not on reels.
I've tested them on the following printers: Replicator 2, Replicator 2X, Makergear M2, FlashForge Creator Pro.
The parts are labeled by internal dimension, i.e. the distance between the reel halves. So, pick the reel appropriate to the width of your SMD tape. Print out two of these parts and screw them together with #2 screws. Sheet metal screws like these work great:
See them in action: