This is a small 17 strand herringbone design done in think black nylon cord. This is quite small and would fit a child or someone with a skinny hand, The weave is relaxed and the knot could be worked up to a snug fit if you have the patience. Note the pen cap in the corner shown for scale.
WhatKnotShop on Etsy
WhatKnotShop on Zibbet
This wider knot is both expandable and adjustable. By adding additional passes of material it will maintain it's approximate size and dimensions. By working up the knot to it's natural finished state it will decrease in diameter as the gaps in the weave are reduced.
Made from 2 mm synthetic cord
Find a rope bracelet like this in one of these shops:
WhatKnotShop on Etsy
WhatKnotShop on Zibbet
This knot has been worked up to it's natural finished state. A single strand of parachute cord has been used in a herringbone weave to achieve the effect of a solid form. The "over two, under two" sequence is worked snug so that the soft core of the cord has taken a set that maintains the shape.
This is the familar three strand rope bracelet that kids love. Usually these are made from a cotton twine that shrinks to fit when it gets wet. This one is made from nylon and must be worked up by removing slack from the knot one loop at a time since nylon doesn't shrink.