Please note that measurements of the bag are external, and internal space is less due to seal and air channel.
You can use this size of bags to get more into hand luggage, although if this is all that is required, you may prefer the simpler and smaller Medium Heavy Duty Travel Rolls. However, they are big enough to use for general purpose packing of normal suitcases. They don’t fit bulky items, but do handle normal clothes fine.
The real benefit of these, as we noted in our introduction to vacuum travel bags with valves, is that you can seal the bags up at home and reduce them using a vacuum cleaner and the turbo valve, and then when you are away, you can use the roll up function to remove the air by pushing it out of the air channel at the bottom. All the functionality is explained in full in the Instruction Booklet on the front of the pack.