Kos consists of alpaca fibers that are combined with wool and blown into a nylon stocking. This results in a soft, light and airy yarn.

Alpaca is about three times warmer than ordinary wool and thus insulates well. The fiber is hollow and breathable, so it feels warm in cold temperatures and cool in warm ones. The wool added to this blend provides resilience and volume. Both alpaca and wool have good heat-regulating properties.