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. Available in 134 colors, So Fine! also makes a wonderful bobbin thread. Here at Quilts on the Corner we love this in our bobbin while using Magnifico or Omni on the top.? It is "so fine" that we can more yards on a bobbin.