Silver Birch is one of the new "Contrast" range of yarns designed to be Double Stranded with Silver Birch Contrast Suri Silk Haze. Check out the "Contrast" page for a Special Twin Pack deal.  Equally this stunning colourway can be used as a stand alone.
4 Ply Merino Nylon is a good sock base is 75% Superwash Merino/25% Nylon.  There are 425 metres per 100g.  Good base for socks but really suitable for any sort of knitting or crochet.   Wash at 30c.