With three separate compartments the main space accessible from the back or top offers effective protection to valuable sensitive equipment, it uses velcro dividers to change the configuration to suit.
An expandable compartment on the front has a drain hole at the bottom and a waterproof barrier separates it from the main compartment useful for wet or dry clothing etc.
Then theres the top compartment where you can gain access to the main space and a storage pouch that can take a 15"  laptop.
Further more there are several smaller zip pockets to store small items and straps and buckles to attach things like  tripods to the outside as well as a waterproof cover that goes over the whole pack.
This is the larger of the Whistler back packs and would suit some one who likes to take a lot of camera, drone, sound & video recording equipment into the field.

More information and reviews are available on you tube and the LowePro site
Grab a bargain these. Are nearly £400 new