12 gauge GXL Red Wire. Sold by the foot.
This wire goes from fuse #4 to the horn relay and is 63 inches long with "wire to spare".
Sold by the foot.
GXL Wire insulation: Cross-Linked Polyethylene
GXL Wire is recommended for use in harsh, high-temperature environments where high heat resistance is required as per SAE J-1128.
GXL Wire is frequently found in engine compartments, trucks, tractors, boats, buses, and general applications where high durability coupled with high heat resistance is a requirement.
Recommended temperature range for GXL: -40C to +125C