The Tonor TW842 is an excellent wireless mic set! I was surprised at how good it is for the price. I have used more expensive wireless mics from more well-known "professional" brands and these sounded just as good or better, and this set was easier to use; just turn on the mics and the receiver, and they sync properly and work right away. Here are the features that were most important to me:- No signal interference.- Switchable frequencies if interference is encountered.- Battery life indicator. Without it, the only indication is a dead mic.- Build quality, designed to not break easily.- Use multiple units.- Mixed audio output to capture all 4 mics with a single (1/4" or 6.35mm) input.- Simple to use for presenters and performers.- Individual audio output to send each mic (XLR) separately to a mixer to adjust or mute on the fly.This wireless mic set is just right for my purpose. I use two units in a church with two meetings running simultaneously. Each receiver has two handheld mics and two body packs (model TW842). The body packs with a headset or lavalier mic are used by a presenter, or multiple presenters, who hand them off to the next one. The two handheld mics are passed around the audience for comments. I walked around the rooms where they will be used to check for interference. The large main room is notorious for interference in the very common 500 MHz frequency band . That was a problem on a unit from a different manufacturer, which I returned to try this one. This one transmits between 900 and 930 MHz and there was no interference at all even with a room full of people with mobile devices, several WiFi repeaters nearby, and a transmitter for hearing-impaired receivers. The range was astonishing. I walked down hallways, into other rooms, and still was able to transmit without dropouts. The long range was a bit of a problem when I initially tried to set up two units on opposite sides of the building. When they're delivered, the mics sync to any receiver, so when I was testing the mics on the second unit, people in the first room could hear my voice. I had to shut it down and figure out how to change channels. That was a little tricky because there's no documentation about that in the box. More on that, and instructions, below.The build quality of the handheld mics is excellent. The metal handheld mics are nicely finished and feel robust, like they're going to last for a long time. The threaded housing for the battery compartment twists on and off very easily and precisely. Another unit I had tried before had plastic handheld mics and the threads on the battery housing were sticky and would have been easy to accidentally cross-thread. The body packs are plastic, but they feel sturdy.Battery life indicators are essential to help me decide if I can keep using a set of batteries for a meeting or if I should replace them so they don't die during the meeting. I haven't tested the battery life, but they have lasted through several meetings so far without needing to be replaced.Two potential improvements I suggest: improved documentation, and body pack antennas that can be replaced.The body pack antennas are small and delicate, as they are on body packs from any manufacturer, but they are not removable and replaceable like some, more expensive, units. When people are adjusting the body pack volume, moving around, putting them on, or taking them off, they can be damaged and that's the end of the body pack. This hasn't happened yet, but it would be nice to be able to replace the antenna without having to replace the entire body pack. The Tonor TW842 is a new product and I'm not even sure if I can replace an entire body pack, or if I have to buy a whole new set. Hopefully I won't need to. One presenter accidentally dropped a body pack because it was just stuffed in a pocket rather than secured with the clip on the back. Luckily it survived. Tell your presenters to use the clips or don't use the body pack at all. The clips will hold the body packs securely if they are used properly. I bought some belts designed to hold body packs for fitness instructors so women in dresses won't have trouble finding a place to put the body pack. They just put the belt around their waist with the body pack secured to it.The documentation is very basic. There were simple instructions to change frequencies using the HI/LO button in the battery compartment of the handheld mics, and the SET button on the body packs, but there was no explanation to set and keep the frequencies when using more than one set. After some trial and error, this is what I learned:The units seem to come from the factory without being synced or paired to a specific receiver. That's great if you have only one receiver. Just turn it on, turn on your 4 mics, and everything works great. If you want to change frequencies (channels), just click the HI/LO button in the battery compartment of the handheld mics, or the SET button on the body packs. The frequency changes on the mic and also on the receiver. The receiver will also show a channel number. The mics only show the frequency. There are 10 frequencies and channels for each mic; a total of 40 for all 4 mics. The frequencies don't overlap so you can theoretically use up to 10 units simultaneously. The mics have a small label on them: A, B, C, and D. From left to right on the receiver, the first (A) uses channels 1-10, the next (B) uses channels 11-20, the next (C) uses channels 21-30, and the last (D) uses channels 31-40.If you turn on a second receiver, it syncs to the frequencies of the 4 mics that are already on, so now two receivers are picking up the 4 mics. If you turn on the other 4 mics for the second receiver, they will also sync to the same frequencies. If you change the frequency on the mics for the second receiver so they won't be picked up by the first receiver, the frequency on the first receiver also changes. The manual doesn't explain how to set up multiple receivers.There are instructions in the Troubleshooting section of the manual to re-sync the mics if they aren't connecting. It turns out that's the secret to setting the frequencies on the different receivers so they stay set and aren't changed by another set of mics when they're turned on. If you are only using one set of mics, you don't need to bother with this. If you add another set, though, you will have to re-sync or pair the mics on each receiver. This seems to lock the mic to the receiver. The procedure is:1. Turn off the receiver.2. Turn off all the mics.3. Initiate pairing. For a handheld mic, hold the HI/LO button inside the battery compartment while you turn on the power. The display will blink to show it's ready to sync or pair to the receiver. For a body pack, turn on the mic and hold the SET button for a couple seconds until the display blinks.4. Turn on the receiver. Wait a few seconds for it to be fully started.5. Pair the mic. For a handheld mic, press the HI/LO button once and it will pair with the receiver. The display will stop blinking to show it has paired. For a body pack, press the SET button to pair it with the receiver.6. Repeat the process for each mic, making sure to turn everything off except the mic you will pair.7. At any time in this process you can press the HI/LO or SET button to select a different frequency/channel and the mic and the receiver will remember that value when the set is used next.For simplicity, I set my first receiver to channels 1, 11, 21, and 31, and I set my second receiver to channels, 2, 12, 22, and 32, but you can select any of the 40 channels, as long as they are different on each receiver.Tonor's support seems to very responsive. I had to contact them about a shipping error and they returned an email quickly and addressed my concern. I figured their customer support is located in a distant time zone from me and I was pleased with the quick response, within 24 hours.Despite the relatively minor concerns I raised, I highly recommend the Tonor TW842 microphone set. It's a quality unit for a great price.