Smooth, lint-free polyester for quilting or embroidery when a matte finish is desired. So Fine #40 is a slightly heavier, variegated version of So Fine #50. Suitable for domestic or longarm machines. Use Bottom Line or So Fine #50 in the bobbin.

Recommended needle:

Topstitch 90/14 (Domestic machine)
#18 (MR 4.0) (Longarm machine)

Recommended top tension:

2.0 - 3.0 (Domestic machine)
Loose on top and bobbin (Longarm machine)