Looks like K&F is branching out from just lens filters. Their batteries and charger are just rebrands, but that's not a bad thing.

This is a review review for the Set/lot of items for camera or Camcorder for sale on AMAZON with the description:
K&F Concept 3-Pack NP-FZ100 2280mAh Battery and 3-Slot LCD Charger for Sony FX3 FX30 A7 III A7 IV A7R III A7R IV A9 A6600 A7R3 A7S III/A7S3 A7C Alpha 9 Alpha a9 Alpha A9 Alpha 9R A9R Alpha 9S Camera.

This is a PACK of charger and three batteries of high nominal capacity, with the possibility of simultaneous charging with a status indicator display for each of them. The power input connection (5v. can be made through both the USB-C and the USB-micro ports, both located on the side of the charger (adapter cable to USB-A included, power adapter not included).
The contacts and battery cases are perfectly adapted to the SONY models that support the NP_FZ100 battery, used by this brand in cameras starting with the A7/III model (which is the one with which I have been able to contrast them), that is the R and S versions (high resolution and high sensitivity) of this same ILCE A7 III model, and also the two versions A9/A9 II, and their “R” versions (high resolution), and at least for a small sensor APSC format version, the latest A6600, and even for a FX·/FX Camcorder models 30.
The biggest limitation is the simultaneous charging time of the three batteries at once, regardless of the power input, simultaneous battery charging can take more than 6 hours, this is not worrying if we leave them all connected in the afternoon at night when we are no longer going to use them until the next day. But if we have some of them discharged and we need the camera to operate in a shorter period of time, then it is better to connect only one of the batteries to charge it in just under half the time (like about 2 and a half hours) and then leave the other two to charge for a period of about 4 hours (all this if we put them on charge after a full discharge).
The stored current capacity of each battery is up to 2280mA/h, and their nominal voltage is 7.4 V., which implies a power limitation of just under 17 W/hour well below the maximum consumption of this type of photographic or video camera.

K&F used to be a budget brand that no one really knew about but now they have really upped their game! I own several of their products. From batteries to tripods and even their various filters. All of them I would consider premium products. The battery charger feels pretty generic like most of them out there. Smallrig, neewer, etc. What makes it different is the 3 charge slots which makes it convenient. I typically carry around 10 batteries with me to film weddings and having a charger that can do this amount of batteries at a time is great! One thing that ticked me off about Sony is they released newer firmware that actually removed the percentage on the batteries if they are not from Sony which left you guessing what percentage they were and you had to rely on only the battery indicator like old school cellphones. So even ones that I bought before that stated they were compatible and gave no errors, unfortunately now do. These batteries however do not give you the warning and retain the percentage for now at least before Sony decides they want to be greedy again. Highly recommend this brand. You won't regret it especially for the price.

If you have a Sony device that is compatible with NP-FZ100 batteries, this pack is a great option. With three 2280mAh batteries each and a three-slot charger, it's perfect for long photo sessions where one battery isn't enough.

➕ Strengths:
- Large capacity: Each battery holds a charge well, with a battery life close to that of original Sony batteries.
- Practical charger: The charger allows three batteries to be recharged at the same time, avoiding waiting to charge them individually. Its clear LCD screen shows the charge status of each battery.
- Portability: Lightweight and compact, it is convenient to carry. It can even be powered via USB, ideal for on-the-go.
- K&F quality: The brand is renowned for its photo accessories, and here again the quality is there.

➖ Points to note:
- Although slightly more affordable than Sony batteries, the price is still an investment; however, the value for money is very satisfactory.

These batteries work as you would hope them to, just as good as the original manufactured batteries. That is good enough right there, but what sets this apart is the triple charger that displays the level of each battery as they charge. This has made charging so easy for me and I love it.

For use with the Sony A7R IV camera, I got the K&F Concept 3-pack of NP-FZ100 batteries and the 3-slot charger. These battery kits have proven very useful for me over the past few months, and I am very pleased with their performance and ease of use.

The batteries appear to have good longevity in terms of how long they can discharge before needing replacement and can fire at least several hundred shots per charge, which makes these on par with Sony branded NP-FZ100 batteries in terms of capacity. I particularly appreciate the utility of a simple LED indicator on the charger that informs on the charge status of each battery slot with green meaning fully charged and red meaning charging. The fact that it’s possible to charge 3 batteries at the same time is good because these cameras drain batteries rather quickly.

The physical construction of both the batteries and charger also appears to be well-engineered – there are no cheap plastic components here. The battery tabs, for example, are nicely click-in with the camera without any possibility to wiggle. But it is even better that the kit has a car charging adapter which can be used to charge batteries in my car whenever I do not have access to an electrical outlet.

Overal for the price offered, K&F Concept offers an exceptional value with this battery kit. It is very stable for my daily use of shooting pictures and the 3 slot charger is very useful. That means I never lack power to supply all my electrical appliances within my home. Definitely the best for those who own any sony mirrorless camera.

This battery and charger set is excellent for my Sony camera. The batteries last a long time, which is perfect for extended shoots. The triple-slot charger is very convenient, allowing me to charge multiple batteries at once. The LCD screen on the charger provides clear information about the charging status. It’s a reliable and essential accessory for any photographer.

Keeping my camera powered has become effortless with this battery and charger set. The three-slot charger is a real time-saver, allowing me to charge multiple batteries simultaneously. Each battery holds a solid charge, which is essential for long video shoots and extensive photography sessions. The LCD screen on the charger is incredibly handy, providing clear indicators of each battery's status. The safety features, including over-voltage and over-charge protection, offer peace of mind during use. This set has significantly improved my workflow, ensuring I always have a charged battery ready to go.

The charger and batteries both worked fine. I didn't have any trouble with them and they are performing to spec with no issues. The charger is easy to charge and I love that I can use a battery bank to charge.

I own a Sony A7RV, and these batteries are compatible. I have no issues at all; they are quite nicely made.
For the price, you get three batteries plus a charger, which is an extremely good deal. K&F has become a very trusted brand, so I feel safe using their batteries on my camera. I would recommend this bundle to anyone looking to save money on spare batteries.