The ESB HR 4C are 2-way coaxial car speakers from the Harmony Hard Rock series, designed to bring balanced audio to smaller installation spaces. Each speaker in this pair features a 100 mm diameter, combining a pressed paper cone woofer with a 13 mm Mylar dome tweeter to handle a frequency range from 80 Hz up to 18 KHz. With a nominal impedance of 4 Ohm and a sensitivity of 87 dB, these drivers deliver a steady performance with 50W RMS power, capable of reaching peaks of 100W. This makes them a practical choice for drivers looking to replace factory speakers with a reliable setup that fits 4-inch slots without requiring extensive modifications to the vehicle's interior.