*Harper Was The First In The Market With The Light Weight Frames Composed Of Glass Filled Nylon.* This Material Is As Strong As Steel Or Aluminum. *All Parts Of The Frame Snap Together Without The Use Of Hardware Or Tools. *Stair Glides Are Built Into The Frame Which Helps To Ease Movement Up And Down Stairs And Over Curbs. *Handles And Base Plate Are Made Of Steel. Optional Accessory Is A Folding Nose Extension, Part Number Pgen21Blk.