From the manufacturer:
Susan Bates Silvalume Afghan Crochet Hooks are made of lightweight aluminum. Each Silvalume hook undergoes a special anodizing process, which etches away all surface impurities. In addition, each hook is heat treated for strength and durability and polished for a velvety smooth finish. Each size is color coded so you can find the size you need at a glance and the U.S. and metric sizes are clearly marked on the knob. These hooks have an extended shaft, which aids in working afghan and Tunisian stitches. This package contains a 10 inch double-end crochet hook.