A straight plug is better when the jack is on the top or bottom of your player.
50% have it
16. has a battery level indicator
An indicator shows you when the device has low battery.
12% have it
17. has a 3.5mm male connector
A standard 3.5mm male connector is suitable for use with all MP3 players and computer sound cards.
83% have it
18. has an on-ear form
This device comfortably rests on top of your outer ears. As it doesn't block out everything from the outside world, it's preferred in places like office environments and recommended for outdoor activities.
23% have it
19. has a removable battery
The battery is removable and can be replaced by the user if broken.