Apple Offering $50 Credit to Customers Who Paid for iPhone 6 and Later Battery Replacements From January to December 2017 - MacRumors
Apple iPhone 6 Battery Replacement Kit with Tools, Video Instructions, Extended Life Battery and Full One Year Warranty - Walmart.com
Apple says iPhone 6s and 6s Plus battery life may vary 2-3% regardless of Samsung or TSMC chip - 9to5Mac
iPhone Battery and Performance - Apple Support
Amazon.com: Battery Case for iPhone 6s Plus/6 Plus/7 Plus/8 Plus 8500mAh, Rechargeable Charging Case for iPhone 6Plus Extended Battery Pack Charger Apple 6s Plus Portable Power Bank Cover for 7Plus 8Plus (5.5”) :
13 battery cases and power packs for your iPhone 6 or 6S - CNET
Battery for iPhone 6 Plus | Replace iPhone 6 Plus Battery