Haven't trail tested 'em yet... but they seem to be pretty sturdy
I have seen the official Molly Mac Pacs....and they are totally bomb-proof and waterproof...mine are not waterproof (or even firecracker proof)...after making these, I would not hesitate to pay $170-$180 for the official gear
The camo one is made from 9oz nylon ripstop and nylon webbing for the MOLLE thingies. shoulder straps are made from additional camo material.
The blue one is salvaged from an 10+ year old alum. frame pack. The material was deteriorating from being in the attic for so long..but the hip-strap was fine....so I kept in one this frame. The shoulder straps are just some rope that is wrapped around iteself