This reduced-sheen monofilament polyester is the best choice when it comes to invisible threads. Unlike other monofilament threads made from nylon, MonoPoly is 100% polyester. Commonly referred to as an invisible thread due to its fineness and reduced-sheen, MonoPoly is great for the bobbin or top. Available in two colors, Smoke (for dark fabrics) and Clear (for light fabrics).
Home machine: Superior Topstitch #70/10 or Microtex #60/8.
Longarm machines: #14