I will have to weigh mine some time. They don't feel heavy, but I don't think I have ever held any other brand, at lest not empty, so I don't have a frame of reference.

If they are heavier than average, it's likely due to the thick sitffners and extensive use of zippers, some of which are chunky. Each rear has two external zippers for the two major compartments. One rear has an internal zipper that can be used to create two separate compartments out of the main one. Each front has one external zipper for the main compartment and one of them has an internal zipper. Each front's outer mesh pocket also zippers shut.