Milian Acoustics ST Miniature Noise Isolation Headphones Low Profile & Super Lightweight only 8 oz.! Collapsible design folds down to 12 x 9.4 x 10 cm 40 mm Neodymium Drivers - Frequency Response: 20-20000 Hz Impedance: 64 Ohms - Sensitivity: 105 db SPL @ 1 kHz 23 decibels of Circumaural Noise Reduction