100 percent cotton thread.
Quilting Thread; New Mettler Silk-Finished Cotton 50 Weight
Mettler Cotton threads for Embroidery and quilting
Mettler Silk Finish Cotton 50 Thread - Large Spool
Mettler Silk Finish 50wt Thread – Red Rock Threads
Patchwork & Quilting - March 2015, PDF, Patchwork