Capacious Extremis

Transform an ordinary small bag/pouch into a Handy Haversack’s central pouch, a backpack into a Bag of Holding, or a trunk’s internal capacity into a Bag of Holding with:

An opening of 3 feet long and 2 feet wide. Internal size of 6 feet long, 4 feet wide, and 4 feet deep. A limit of 1000 pounds and 150 cubic feet.