Update 2024: still 5 stars, been using them 3 years and still work great. Now running them sometimes for off road riding, it's nice to be able to communicate with riders in my group without having to stop and shut off engines. We've had 4 or 5 all connected at once, they work fine.Customer service very good also. I had an issue where one unit got damaged and they handled it as well as you could ask for.I suggested them to a friend for him and his son to use, he just ordered 2.These intercoms are very impressive for the price. I bought the two pack and I like them a lot so far. I installed in my old helmet (Bell Star 2010) and my new Shoei RF-SR. Both installations were fairly simple. The Bell required installing the base with VHB tape due to the shape of the helmet near the bottom. The Shoei works fine with the included steel tension clip that slides between the shell and lining of the helmet.I initially had problems getting volume loud enough since I wear earplugs when I ride. I think part of it was the Bell Star, it has a lot of vents and isn't known as a quiet helmet. I switched to the Shoei which helped somewhat, and I also switched to Alpine MotoSafe earplugs. This combination works pretty well.I find these intercoms easy to use and am quite impressed with them. Blutooth pairing to my phone and to each other is fairly simple. I'm able to talk to my passenger easily. When we're done talking I just hit the button once and the intercom mode ends and the music resumes if I had it playing previously. I'm able to make calls using voice control with my phone. The person on the other end of the call hears very little noise, sometimes they don't even realize I'm on a motorcycle. It's better sound than the blutooth mic in my car.I haven't tried these bike-to-bike yet, but I was able to talk to my son while he was riding around in a big parking lot. I was standing and I kept my helmet on so I could coach him while he was practicing, it worked great. We stayed within about 150 yards so I can't comment on longer distances yet.Customer support seems very good on these. I contacted them about insufficient volume. After suggesting some things, they thought it might be a faulty speaker harness so they sent me a replacement. I don't think that was the problem, it was more of a bike/helmet noise issue, but they definitely tried to help.I rode my streetbike (FZ1 Yamaha) about 3-4 hours today. Played music almost the whole time and had 3 phone calls totaling about 10minutes. When I got home I pushed the two volume buttons to check battery level- it was still over 90%.If the M1S Pro units last a few years then I'd say they were well worth the cost.