Singer Bobbins For Models 27, 28, 127, 128 Bobbins are in 5 pack
Outside diameter: 33mm - Height: 9.4mm - Axis diameter 2.5mm
singer 128, singer 127,singer 27,singer bobbin
shuttle

Never wind thread onto a bobbin that already has thread on it.
If there is thread already on a bobbin and you need to use a different color or thread type then use a different bobbin or remove the existing thread from the bobbin before you wind new thread.
The reason is that the end of the existing thread may get tangled in the new thread and jam your bobbin or cause other problems and also the new thread will not wind evenly over the old thread and therefore will not unwind evenly during use and will cause tension problems.

Center tail – After you wind a bobbin you must cut off the end of the thread that is coming out from the center of the bobbin.
This must be cut off close to the bobbin so that there is no tail of thread sticking out.
A thread tail can interfere with bobbin rotation and cause tension problems.

Over filled – Make sure your bobbins are not over filled with thread