Made of lightweight aluminum, each Silvalume hook undergoes a special anodizing process, which etches away all surface impurities. Each hook is heat treated for strength and durability and polished for a velvety smooth finish. Head helps reduce wrist motion for fatigue free crocheting and helps you maintain a more consistent gauge. Hooks measure 5-1/2 inches. Conversions are size B/1 = 1.25 mm, size C/2 = 2.75 mm, size D/3 = 3.25 mm, size E/4 = 3.5 mm, size F/5 = 3.75 mm, size G/6 = 4 mm, size 7/7 = 4.5 mm, size H/8 = 5 mm, size I/9 = 5.5 mm, size J/10 = 6 mm, size K/10.5 = 6.5 mm, size L/11 = 8 mm, size M/13 = 9 mm, size N/15 = 10 mm.