#50/2 extra-long staple Egyptian-grown cotton on cardboard-sided M-style bobbins.  148 yds

Cardboard-sided prewound bobbins may be used with the cardboard sides on or with the sides removed.  Please experiment to determine what works best in your machine.

Below is a partial list of machines compatible with the M style bobbin:

A-1
Gammill
Handi Quilter - Sweet Sixteen
Homesteader
some Noltings
Tin Lizzie 18
Innova
Baby Lock Crown Jewel
Viking MQ 18X8
Pfaff GQ 18x8