I'm still learning.... guessing that LB stands for long bed?? don't know about the initials OW?? I first ordered the less expensive FM foot that was all plastic. Needed to remove the part that cuts the thread to allow more room for that foot. Hated it! Went ahead an ordered the all metal one and LOVE it. I learned from so many of you that the 301A's are great machines for fmq, which I so much want to keep learning. Thank's to everyone here whom I keep learning from.