Consider purchasing the battery from an authorized Apple service provider or Apple itself. Apple provides genuine and certified replacement parts.
Look for batteries that are labeled as OEM or original. These batteries are manufactured by the same company that made the original battery for your iPhone.
Read customer reviews and ratings for different replacement batteries. This can give you insights into the performance and reliability of a particular product.
Check the battery capacity. Aim for a replacement battery with a capacity similar to or higher than the original battery. Higher capacity generally means longer battery life.
Ensure that the replacement battery is compatible with the iPhone 11 Pro Max. The battery should match the model number of your iPhone.