Dometic 8700 Torsion Spring Assembly, also suits both the A&E 8500 awning and the A&E 9000 awning.
You can fit 8700 springs to an 8300 tube, however both require changing over as you can not use one of each. It may be cheaper to purchase a new awning with roller tube, vinyl and both springs.
RH (Right Hand) side is the one with the open/close lever.