The Sigma, Alpha and Beta Bags feature: A closure assist flap on the main compartment.  Snap down storm flap on the main compartment. Large #9 YKK zippers on all compartments with dual sliders. Continuous wrap around carrying handles for superior weight support.  Metal "D" rings on the side for tying clothing or equipment to the outside of the bag.  Two detachable padded shoulder straps for three carrying configurations: 1. Suitcase 2. As a shoulder bag 3. Hands free backpack style.