I first connected my Bose QC 35 headphones, it went very smoothly, worked immediately. The next time I turned on the headphones, the BT100 recognized immediately and worked without manual intervention. I also connected my other Bose QC Earbuds II, it didn't work. I was sweating, finally I decided to do a reset on both BT100 and Bose QC Earbuds II (ie remove all paired devices). Then I started by pairing the BT100 with the Bose QC Earbuds II now they found each other better. Then I also paired with Bose QC 35, it went very smoothly as usual. Then the next problem came when I wanted to listen to the Bose QC Earbuds II, when the BT100 didn't connect automatically, I had to press the button on the front then it starts looking for paired devices and then found my Bose QC Earbuds II. BT100 has bluetooth version 4.2, Bose QC 35 has bluetooth ver.4.3 and Bose QC Earbuds II has bluetooth version 5.3. So in summary, the BT 100 works smoothly and well with bluetooth devices with ver 4,.....but works worse with device bluetooth ver. 5.3. I still give four stars because that the sound quality is good. I have to live with, that when I listen with devices that have bluetooth ver. 5..... then I get to press the button on the front to initiate a search of paired devices.