A shoulder strap pad will help keep your backpack from hurting your back as you travel around during the day. The strap should be cushioned and keep the bulk of the impact off of your shoulders acting as a shock absorber. You will feel much better at the end of the day with a cushioned strap. If you do not know where to look, then you can go to your local sport’s store to see what they have to offer. They will have them in many colors and styles to match the bad you have. You may even get more then one if you want. Your back will thanks you!