So Fine 50wt 3280yds 403 Putty is a 50 wt. 3-ply polyester thread. Designed for bobbin thread, quilting, and sewing. So Fine! is a lint-free, matte-finish, smooth 50 wt. 3 filament polyester thread. Due to its fine nature, So Fine! is an excellent blending thread and loved by both longarm and home machine quilters. So Fine! also makes a wonderful bobbin thread. Recommended Needle Size: 80/12.