Price
Quality plug wires with a stainless steel spiral wound core. Much higher quality than stock and a limited lifetime warranty.
8.5mm wires have 13% more conductor than 8mm for less voltage drop. Stock wires usually last 20,000-30,000 miles and are possibly the only weak link in the Miata drivetrain. No RF interference. Red in color.
Fits 2001-05 engines including the Mazdaspeed. Since the coils sit directly on two of the plugs, there are only two wires.