Packing cubes or compression packs really serve two purposes. Firstly they keep your pack well organised. They make it easy to find an item without having the chore of rifling through your entire pack when you need to find something. A plastic bag can do that, so what separates them and makes them desirable is their compression and shape creation properties.
Shape creation makes packing a lot easier. You spend a bit of time figuring out how best to fit everything in, but once you have that layout you can repeat it because everything remains more or less the same shape. You can’t do that very easily with a plastic bag.
Compression effectively adds space to your pack. Manufactures claim up to 50% by volume space reductions when using these products. In the real world you are going to get somewhere around 40%, but consider what a difference that can make to your 70 litre pack, if you were able to fully compress the contents it turns it into a 98 litre monster. In reality, you are not going to do that but savings are still there to be made.
I personally use four of the Eagle Creek packs (2 t-shirt, 2 underwear) and one larger Osprey for my waterproof jacket and warm liner. This gives me approximately 17 litres additional space. For the rest of the pack I use a few of the cheaper cubes you can get in sets for around £20 on Amazon. These generally include three or four cubes, and they provide shape and a tiny amount of compression when fully loaded.
A word of warning
Watch the weight. While compression cubes are great for maxing out the load capacity of your pack, they will obviously not reduce its weight. Start out with a investment in one or two half cubes and test out your pack with it. You might find you hit your desired max weight threshold before you run out of actual space. It’s senseless spending quadruple the price on a good compression cube when a budget one will get the job done.
Eagle Creek Pack-it Specter Compression Half Cube
This was the first type of “proper” compression cube that I purchased. It’s not particularly big, but it does perform well. You will mainly want to load this with T-shirts or underwear.
The manufactures claim up to 50% volume compression with this cube, and with the right type of garment that is certainly possible. In the photos below I managed around 58% of original volume with 4 XL T-shirts.
Compressing takes place by zipping up the outside of the cube. Depending on the garments and how full it is this can be a simple task, or one that requires you to squeeze the pack between your legs and fight the zipper while cursing your choice to overload it.
Osprey 12 litre straight jacket compression
For larger compression cubes I swap over to Osprey. While the zip solution works well for smaller cubes I don’t think it’s quite as effective with larger ones.
The Osprey straight jacket cubes use clip fasteners and compression strapping to reduce the bulk of the contents. I use one of these to reduce my waterproof jacket and warm layer down in size.
With this particular load I managed to get the cube down to 63% of it’s original size which is a considerable saving. The cube also fits nicely at the “bottom” of my Farpoint 70 pack which is where I want it given I wont need the contents that often.
You can pick up a 12 litre version of this cube at Amazon for around $27 (US site only at the moment).
Osprey 12 litre dry sack
This is not really a compression sack, but it fits the narrative of this section as the dry sack can compress a little and does provide shape.
I use this for storing and washing dirty laundry. It is waterproof, so keeps the smells secure when you are transporting dirty items and allows you to wash them in it without getting your hands soaked in detergents. It also packs down to nothing when empty, which is a major bonus. Sealing is a accomplished by folding the top over on itself and clipping. I find that if you get the top flush and folded over once you can put your arms on top of it against a solid surface and drive the air out while you seal it, this way you can get a moderate amount of compression into the bargain as well.
I have two of these now, the second one serves as a waterproof jacket for my laptop sleeve.