The Rear Rac Pac II has a roomy main compartment, a side opening pocket in the top flap, our secure five-point attachment system, 1-2" 4 lb. foam padding on all six sides, 3M Scotchlite Reflective Material across the back end with a section for attaching a clip-on light, and D-rings front and back for attaching an optional shoulder strap. By far the most ingenious addition to the bag is an expandable zip-open baffle, which allows the top of the bag to tilt up and increases the main compartment volume by 52%. With the baffle fully unzipped you can fit just about anything in this bag but the kitchen sink. Jandd has also added a couple of hook and loop straps on one side of the Pac for ease in securing a tire pump. The material used in the Rac Pac II is Hydrothane-coated for superb water repellency, every possible seam is taped, and storm flaps protect every zipper to ensure that no moisture will get in unless you put it there yourself