I have 3 wood thread spools, the wood painted black with a bit of off white/tan thread on them (it is more of a light weight yarn).  They measure about 8 7/8" in length x about 1" across the top & about 3/8" across the bottom.   2 have brass caps on the top of the bobbin. They are in nice condition.  These are a vintage item.

3 wood Thread Spools / bobbins Vintage