For sale is the right (R) side only of the WF-1000XM4. This is a used item, but the battery has been replaced with a new genuine Z55H battery, and has been tested and cleaned. You don't have to worry about the battery degradation that is common with this model. Please check the photos for scratches and stains. We have confirmed the operation, but if there are any initial defects, we will accept returns if you contact us before leaving feedback. For those who have a broken or lost one side. The version is the latest 2.1.0. You cannot pair unless the version is 2.0.0 or later, so please check your current version before purchasing. Pairing instructions for those who have purchased only one side: Place the left and right earbuds in the case and insert the USB cable. It will blink red rapidly 3 times, so press and hold the touch sensors on both the left and right earbuds (for about 10 seconds) until it blinks red slowly. Once it blinks red slowly, release your fingers and initialization & pairing is complete when it blinks green 4 times. Delete the previous device information from the Bluetooth settings of the connected device and re-register.