The Bag of Holding is a small pouch that is bigger on the inside than on the outside and always weighs one pound no matter how much gear it carries.
The bag does have a limit to what it can hold however. It has 20 cubic feet of storage space and cannot carry more than 200 pounds of gear.
Haverford's Handy HaversackEdit
The powerful wizard Haverford created an improved version of the Bag of Holding. By using magic to enchant a haversack, he invented a new magical item which could hold 1,000 pounds in weight or 100 cubic feet in volume of gear, yet it always weighs only one pound.