Air means its ultralight, made with 30D hybrid sil-nylon CORDURA. Vent means it purges air through the eVent bottom. Dry means its factory seam sealed with a roll-top closure, the rolling stay is pre-curved so that it pops open, making it easier to load than a flat stay. Bloc means it nests inside your pack well. Solid means its durable, and also that you can compress your gear down to a nearly rocksolid state. But the name doesnt quite say it all, Granite Gear has lightened it up by replacing the compression webbing with paracord. They call it LineLoc Technology, another Granite Gear first.