Dragline silk's toughness of roughly 160 MJ/m³ exceeds Kevlar's several-fold because the fiber stretches up to about 30% before breaking.
Spiders are too territorial and cannibalistic to farm, so recombinant silk proteins are produced in bacteria, yeast, and even the milk of transgenic goats.
When wetted, unrestrained dragline silk 'supercontracts', shrinking in length by up to half.