3mm。 AKG71 is available in white and gray colors, with brown artificial leather headband, giving people a fresh, elegant and retro feeling. The edge is chrome-plated, and the thickness of the leather headband is 3mm, which can be adjusted automatically. AKG (Chinese trademark: AKG) is one of the well-known brands in the audio field and one of the four largest earphone manufacturers in the world. These three letters of AKG are the representatives of professionalism and sound quality.