The bobbin thread is also often called as "under thread, bottom thread".
It can be 100% spun polyester 60/2, 80/2, 50/2, and also be poly/poly corespun 45/2, 59/2, and cotton 60/2, etc.
The length on the big cones can be 10000 yards, 15000 yards, 500grams, etc.
Main colors are white and black, of course, other colors can be dyed specially.
They are suitable for the economical embroiderers who prefer to wind their own bobbins instead of using pre-wound bobbins thread.