Sea to summit ultra sil duffle bag blue description the ultra sil duffle bag is the ultimate in lightweight bags with an incredible capacity of 105 gallons 2420 cu ins 40 liters and strong enough for a heavy load it is the perfect bag as an airline carry on for impromptu excursions or just going to the gym super compact and super light it is an obvious choice as a spare bag on any trip features 105 gallons40 liter volume capacity and strong enough to carry a heavy lo