1. Size: 0.5", 1", 1.25", 1.5", 2", 2.5", 3", 4" 2. Material: Aluminum, Pure Oxygen-free Copper 3 ... 4 lays Round wire coils, Production sizes are from Φ5.0_Φ200mm.Round wire coils include 2 layers, 4 layers ... side of the bobbin essentially an internal / external voice coil. For multi layers of four or more. For flat ... winding designs in order to meet the customers needs. High quality Voice Coil