100 Denier ultra strong Gel-Spun-Polyester thread.
Used by many of the best bass bug fly-tyers. Available in black and white only but can be coloured with markers. Will cut you so be careful.
For optimum useage you should use ceramic bobbins. We advise to always keep the thread tight when you are going to cut or cast off, serrated blades will help cut the high tensile fibres, but tension is the key to nice clean cuts. If you have them, a pair tungsten carbide scissors are recommended but not necessary.