The battery has been replaced with a new genuine one (Z55H). Operation has been confirmed, so please purchase with confidence. Regarding returns, we cannot accept them unless detailed information is provided. There have been cases of swapping and returns after one month of use, so please check the photos and make your purchase. You can use it comfortably with battery life similar to when it was new. Alcohol disinfection and cleaning have been completed. Please refer to the photos for the appearance and detailed condition. ■ Version Information Updated to the latest version 2.1.0 Pairing requires version 2.0.0 or higher. Please check the version you have before purchasing. ■ Pairing Instructions for Those Purchasing Only One Side ※ Be sure to charge your charging case before initializing. If the charge is insufficient, the green light will not blink after the red light blinks. Set the left and right earphones in the case and connect the USB cable. Press and hold the touch sensors on both the left and right earphones for about 10 seconds. Release your fingers after the case blinks red. Initialization & pairing is complete when the green light blinks 4 times. Delete the old information from the Bluetooth settings of the connection destination and register it again. This product is recommended for those looking for only one side or those concerned about the battery condition. Please consider it. Sony Model Name...WF-1000XM4