general driver size : 30 mm / 1.18" dynamic driver power supply : 5 v 1 a maximum operation temperature : 45 °c audio sensitivity : 80 db spl@1 khz frequency response : 20 hz - 20 khz impedance : 32 ohm maximum spl : 81 db microphone sensitivity : -40 dbv/pa@1 khz dimensions net weight : 122.2 g / 0.269 lbs ear cushion outer length (mm) : 67.5 ear cushion height (mm) : 16.28 ear cushion inner length (mm) : 28.5 ear cushion inner width (mm) : 28.5 cable length : 20cm control and connection bluetooth version : 5.3 bluetooth profile : a2dp v1.4, avrcp v1.6.2, hfp v1.8 bluetooth transmitter frequency range : 2.4 ghz - 2.4835 ghz bluetooth transmitter power : (eirp) bluetooth transmitter modulation : gfsk, π/4 dqpsk, 8dpsk supported formats : .mp3, .wav, .wma, .flac battery battery type : lithium-ion battery (500 mah / 3.7 v) charging time : < 2 hrs from empty music playtime with bt on : up to 50 hrs talk time : up to 29 hrs what's in the box 1 x jbl jr 320bt headphones 1 x usb type-c charging case 1 x sticker sheet JBL Junior 320BT headphones offer safe, customizable sound (max 85dB), a 50-hour battery, built-in mic, and a kid-friendly, personalized design. Store in a cool dry place. China