Developed with Semperfli Ambassadors Paul Procter and Hans van Klinken specifically for fly tyers. Semperfli Classic Waxed 12/0 thread is extruded polyester with approximately 17.25 oz. (490gm) breaking strength and is slightly more loosely twisted for a flat profile, giving more grip and less bulk than other threads. 240 yards of 70 denier thread per spool, provides incredible value to the fly tyer. Lightly waxed, easy to split. Excellent for hook sizes 10 to 20.