The beads are strung on a rugged four ply nylon thread and worked through the center of the bracelet. Check this blog posting to see how the center strand is added to complete the bracelet.
Size for this one is "large" 8 1/2" (211 mm) partly due to the presence of the beads. They don't compress the same way that a center strand made of cord would so the overall size tends to increase.
design and photographs © copyright 2013 WhatKnotShop