On the outside of one of the muffs is a black cover that is the battery compartment. You need to pop it off to replace the batteries.
The Howard Leight Impact Sport Earmuff features approximately 350 hours of battery life.
The manufacturer does not state where the Howard Leight Impact Sport Earmuffs are manufactured. For that information I recommend contacting Howard Leight.
Yes, they can.
Yes, they are authentic Howard Leight earmuffs.
It will depend on what kind of parts you are looking for. If you are looking for ear cups we do offer those, but if you are looking for internal replacement parts or something else you will most likely need to contact the manufacturer for most parts. Here's a link to the replacement ear cups:
https://www.opticsplanet.com/howard-leight-replacement-ear-cup-cushions-for-impact-sport-and-impact-sport-bol.html
The NRR rating is 22 dB.
Both Howard Leight/Honeywell and Caldwell hearing protection are manufactured in China.
The specifications do not provide an amplification range or specifics on how much amplification it provides. The documentation focuses on amplifying the ambient sounds like talking or music while cutting off sounds over 82 Db, which can be harmful to your ears. There is a volume control to allow you to adjust it for your needs.