This repair guide is super easy and detailed to follow. My battery problem for earbuds is now gone. I purchased one pair of Z55H battery from Aliexpress ( https://tinyurl.com/26k83wq9 ) at $7-8 and went ahead following the step-by-step guide. It was successful. The hardest part was the step 1 to open the earbuds. I used hair drier more than seven times for 20 seconds each, but ended up using a screwdriver provided by Aliexpress package. There remains a minor scratch on the earbuds, but that's fine. Even after listening one hour long, it is only down to 97%. I am fully satisfied. I am lucky to find this posting. Thanks a lot.