Is the Helly Hansen Guide Duffel 30L waterproof?

Yes. The polyester ripstop shell has a waterproof finish that handles rain and splashes. The zipper is the weak point in heavy, sustained rain.

How big is the 30L version?

It measures 30 inches across and holds about 30 liters. That fits a weekend of clothes or a full gym kit, but not a week's packing.

Does it have a shoulder strap?

The listed setup is a hand-carry duffel with a main zip and an inner pocket. Check the bag itself for a detachable strap before you rely on shoulder carry.

What can I fit in the inner pocket?

It is a small pocket for keys, a phone, a wallet or travel documents. It keeps them off the floor of the main compartment.

Is it good for air travel?

At 30L it is well under most carry-on limits, so it works as a personal item or a light cabin bag. It is not a structured suitcase.

Gym-goers, weekend travelers and outdoor users who want a tough, water-resistant bag. Shoppers wanting lots of pockets or padded straps should look at travel-specific duffels.