thin rubber cord. by the foot. Solid - not a hollow tube. Might even be a shade thicker than 1.5 - like, 1.7mm. Maybe it gained weight on the trip. That usually happens to me.
A polymer clay friend tells me they use this in polymer clay, for loops for hanging - it embeds in the clay and can be fire at the temps that polymer clay cures at.
By the foot. Insofar as is possible and stock permitting, we will ship your order as one entire piece.