Brilliant batteries they hold a charge really well and used in conjunction with the original Sony NP-FW50 taking all 3 batteries out on a shoot you'll do well to get through all batteries in a day - I've frequently taking the newer batteries out and shot over 1000 photos a day with some charge left in at least one of the K&F Concept batteries after exhausting the original and one of the K&F Concept brand - very nice packaging it all arrives in with usb lead and documentation thats easy to read no dodgy Chinese interpretation of words which gives you confidence on electronics when you get them we've all seen them ' power is excellent for making photo safe in your world ' ! etc , and the charger itself hugs the batteries nicely whilst on charge no 'flopping about' once clicked in , the LED's are easy to read going from very bright red to green when charged , charging is pretty quick too the original 'in camera' charge on the Sony A6400 is pants - a fiddly micro usb and a dim orange led thats hidden under said usb that you can't monitor unless you pick the camera up to eye level ( come on Sony you need to sort this one out - amazing camera but sack the charging designer guy tho lol )
I fully intended on purchasing second set of 'K&F Concept's' after making sure these ones worked OK but won't be needing to as I personally as a hobbiest rarely take more than 1000-2000 shots a day , even when I've used them abroad on a shoot I've never been without charge whilst roaming and charged them when I've got back to a Hotel - I thoroughly recommend these batteries and charger and I'm pretty fussy when it comes to putting cheaper batteries in my hard earned 1000 quid camera :)