What does it mean when your iPhone's battery health says Service?
Battery repair for Apple iPhone 6S | Exchanging battery - Part Expert
Amazon.com: EMNT 5500 mAh Battery Compatible with iPhone 6s High Capacity A1633/A1688/A1700 Battery Replacement 【New Version】 with Repair Tool Kits and Instructions【2 Years Warranty】.! : Cell Phones & Accessories
iPhone 6s Plus Battery Replacement - iFixit Repair Guide