The Ergon packs come in three sizes, I ordered the small version for both my hubby and myself. They arrived yesterday. Well worth the $155.00 CAN! The weight of the pack sits on your hips... you don't feel any weight on your back or shoulders..... it feels like the pack is empty. There is separation between the pack and your back, which allows lots of airflow so I shouldn't get overheated.

Ergon put a lot of thought into creating their packs, I highly recommend them!