Packing Cubes
I used these for the first time whilst walking the Coastal Camino from Porto to Santiago de Compostela. As the walk involved staying in 15 different hotels for a noght at a time, I found the cubes invaluable for sorting out my clothes for each day. Can't think why I haven't used them before and the addition of a waterproof section for damp clothes was a blessing. Highly recommended.