Brother PRWB135 Magnetic Core Prewound L Bobbins 100x60wt Poly Thread 100 Pack For Use With: PR-600, PR-600II, PR-620, PR-650, PR1000, Babylock EMP, BMP, ENT10, BNT10, EMP, BMP Patented magnetic core creates unmatched tension uniformity. High tenacity 60wt polyester yarns. Lower cost per yard based on usable yards per bobbin. Bobbins come with 135yds per bobbin.