WF-1000XM4 Maintenance Item This is a used item, but the earphone batteries have been replaced with genuine Z55H batteries. It has been tested and cleaned as a maintenance item. You don't have to worry about the battery degradation that is characteristic of this model. Please check the photos for scratches and stains. The version is 2.1.0. Accessories include the instruction manual, USB cable, and silicone ear tips in S, M, and L sizes. It will be shipped via Nekopos (a Japanese delivery service). If there are any problems, please contact us before leaving a review, and we will accept returns, so please feel free to purchase. IPX4 water resistance. Enjoy music without worrying about rain or sweat. Improved connection stability with the integrated processor V1. Improved battery performance. Supports battery sharing from smartphones. Significantly enhanced call performance. Advanced audio signal processing with four microphones and sensors. Improved fit to the ear. Ergonomic surface design increases the contact area compared to the previous model, achieving stable wearing. Significant improvement in noise cancellation performance. Achieves industry-leading noise cancellation. Significantly improved compared to WF-1000XM3. Wind noise is also significantly reduced. Integrated processor V1 and an evolved 6mm driver, LDAC compatible. 360RA compatible. Achieves overwhelming high-quality sound.