The General Use backrests are for comfort and additional support.  These backrests are great at providing additional padding you would not receive with the backrest upholstery you will find on a wheelchair.  General Use backrests can also be usefull to those who propell their wheelchair with their.  The backrest can work to provide a firm support while "peddaling" rather than the user sliding in their seat due to an upholstered back which may eventually sag.  General Use backrests are also either easy to remove so the wheelchair can still fold or as on some models, will allow you to fold the wheelchair with the backrest still intact.