Sennheiser CX 400BT Series Instruction Manual page 6

Product overview
6 | CX 400BT True Wireless
Earphones
CX400TW1 R and CX400TW1 L
Touch control panel
Changeable silicone ear adapters
Left earbud L (slave earbud, receives signals from the right
earbud)
Status LED
Magnetic holders
Charging contacts
Microphones for phone calls
Right earbud R (master earbud, controls the Bluetooth con-
nection to the smartphone and to the left earbud)
Openings for acoustic optimization
Built-in rechargeable battery