Ideally you want a genuine HP battery. However, many of the same factories that make genuine laptop batteries for HP, Dell, etc also make aftermarket batteries and sell through eBay, amazon and their own online storefronts. I have used the aftermarket compatible batteries many many times and they are generally very good. Buy from a seller with high star ratings and a high number of recorded transactions and you will be fine. At a certain point in the lifecycle, aftermarket batteries are all you can get and if you are offered a genuine battery on say a 5 year old laptop it may either be counterfeit or old stock.
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