Wearing the headset
-
Insert the headset units into both ears.
Put the unit with the
(left) mark on your left ear and the unit with the 
(right) mark on your right ear. The left unit has a tactile dot.
A: Tactile dot
-
Twist the headset to slide the earbud deep into your ear.
Hint
- The earbud will be easier to slide deep into your ear if you pull up on the top of the ear lightly while twisting the headset.
If the earbuds do not fit your ears
M-sized hybrid silicone rubber earbuds come attached to the left and right units of the headset at the time of purchase. If the earbuds tend to come off or you feel that there is insufficient low frequency sound and a difference in volume between the left and right units, change the earbuds to another size to comfortably and snugly fit your left and right ears.
https://helpguide.sony.net/