The present invention involves the provision of a backpack frame assembly and associated load carrying devices. The backpack frame includes a plurality of stays having flexible joints therebetween. A membrane is secured to certain of the stays and helps resist flexing of joints between adjacent stay end portions. Load carrying devices may be provided and are releasably mounted to the frame assembly. The distance between the assembly's shoulder straps and hip belt can be adjusted to accommodate user's having different torso lengths by using an adjuster sheet to separate hook and look members attaching a shoulder strap assembly to a frame assembly. The adjuster sheet can operate as a support element when not operating as an adjuster. The adjuster sheet can be constructed of a laminated composite material and include reinforcing ribs formed therein.