The fundamental geometry and conductor compliment of Type 4 hasn't changed since 1995 because any change to the size or position of the 4-Series' 2-sized Spread-Spectrum conductor arrangement would reduce performance. Type 4 employs Carbon-Loaded insulation (absorbs RF) on the negative conductors and Nitrogen-Injected PE (minimal dielectric involvement) on the positive conductors. In addition, Type 4 includes all Solid Long-Grain Copper (LGC) conductors.