Tested with my phone: iPhone 8 plus. Positives: very good seller's service, Bluetooth connection stable and reliable. Negatives: After reading a lot of positive reviews I ordered this headset without any doubts. Than came the big disappointment. Callers and my voice on other end sounds hollow with limited frequency range - no HD sound at all! If somebody calls me or I call somebody, my voice is transmitted quietly for the first 8 seconds, then the headset starts to increase volume to normal level. Callers can immediately identify that I'm not using my phone. I also have a 4 year old 20 EUR Jabra headset and AERSI K10 is 2 steps below in sound quality. Big disappointment for me, please do not waste your money. If I had possibility to send it back I would do it.
Not bad, mic doesn't have noise cancellation feature for calls.