75% wool and 25% silk, comes in 100g skeins costing around a tenner each. It seems to be two strands twisted together - you can separate them if you try but it doesn't come apart on its own. The colour changes along the length of the skein. I have no idea how they dye it; there's no sharp boundary between colours. The thickness varies but this isn't hugely apparent in the finished garment. It is lovely to knit with. You do need to be a little bit careful with it as before it's knitted it breaks easily. I've broken it by accident a few times while tugging on it fairly gently to tighten up stitches at the ends of rows.