An L-shaped plug is better if the jack is on the left or right side of the device, so that the cable isn't bent, and is less likely to break when the device is in your pocket.
30% have it
16. has a 3.5mm male connector
A standard 3.5mm male connector is suitable for use with all MP3 players and computer sound cards.
81% have it
17. 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.
22% have it
18. has a removable battery
The battery is removable and can be replaced by the user if broken.