The file 'Tailfin Bike Rack Adapter 3D Printer Model' is (stl) file type, size is 79.5KB.
These adapters are intended to space out tailfin racks so that there is room for the seat (on small frames) or room for the seat to lower when using a dropper post on larger frames.
If you need a different diameter or length, here are the original design files in onshape:
https://cad.onshape.com/documents/f4496d1e10b226a0432ea419/w/b918f3f079c0b08ac25c6200/e/9319f568e0d4e9d713f830e0?renderMode=0&uiState=6644f9077e36231fafde2eaf
27.2mm_Tailfin_Adapter.stl | 118.8KB | |
30.9mm_Tailfin_Adapter.stl | 172.2KB |