Why do Wheelchairs have Casters?

The front wheel is also called caster. The small wheel make wheelchair easier to move and change the direction of wheelchair. Also, it's necessary that front casters can keep balance of the whole chair body. While some of the wheelchairs equipped casters in the back of the chair body. Two casters in the front, another two in the back, it's called mid wheel drive wheelchair. This kind of wheelchair keep the gravity in the middle of the chair body. When you want to change directions, you don't need to reverse your chair or need more space, you can directly turn on its own axis.