The cord I use is twisted nylon (usually C-lon or Superlon brand) and is available in four different sizes. I favor the middle of the road size, which is .5mm in diameter. It will fit through an 11/0 seed bead and an 8/0 bead will accommodate two cords. Fiber in Jewelry: Micro Macrame
Hints and Tips for Macrame by Sherri Stokey
A beautiful way to turn those pieces of sea glass you find into jewelry.