ViSang VS-R03 InEar HI-FI Noise Isolation Ear-Buds Earphones Driver units: 10.7mm (CCAW Drive units) Rated impedance: 20+/-10%(Rated impedance) Sensitivity: 115dB (at1000Hz 1mW 20upa) Frequency: 20-20,000Hz Channel Balance:2dB (at1000Hz)