The Thunder series of packs combine traditional top loading access with a full panel opening. This allows total access to gear along the trail and ease of packing in camp.
When fully locked down for the trail, Thunder appears to be simply a traditional top loader. But hidden there on the outside of the pack are two vertical zippers and a horizontal velcro closure at the top. You can see these features pretty clearly in the top photo. Merging these two ways of loading a pack works beautifully. The top lid can be extended to quickly and easily accommodate oversized or overflow items on longer trips. While packing in the morning the zippered panel can be fully opened to make stacking stuff sacks and other gear very straightforward. And during the day access to the bottom of the pack is just a quick zip away. Additionally, there's a stretch panel on the outside where a wet jacket can be stuffed.
So, both sizes of Thunder, 50 liter and 70 liter, are very lightweight and easy to organize trekking/backpacking packs, but they also perform well in mountaineering environments. Side compression straps, stretch side pockets, daisy chains, dual axe loops, tough 210 denier ripstop fabric and a stout and comfortable suspension system lend themselves to taming the extra gear for the high mountains.
Available in women's and men's suspension systems and 50 and 70 liter volumes.