The Shure Aonic 50 Headphones are slightly bigger with 50mm headphone drivers, available in more colours such as Black, White and Brown It also Supports LDAC codecs which allows you to stream high-resolution audio up to 32-bit/96kHz over Bluetooth and has 20 hours of Battery life. The Aonic 40s have 40mm drivers, is available in Black and white, are completely collapsible so you can easily transport them and have a 25 hour battery life.