Clicking though their 'ultra light packs'

The kids pack is 2lb, 4oz. https://www.rei.com/product/870881/rei-passage-38-pack-kids "I bought this for my 8 year old daughter's 1st backpacking trip."

And that's more than twice as heavy as his pack.

PS: Sure on it's own saving 1lb is not that big a deal. But, if you focus on saving a few ounces here and there it makes a huge difference.

when places like REI use the term ultralight, it means an entirely different thing than how an experienced backpacker thinks of the word. To an experienced backpacker, rei (or any chain) does not carry ultralight gear. There is an entire market of specialty gear makers making true ultralight gear and none of it is in retail brick and mortar.

I use this as an ultralight pack: https://www.rei.com/product/892074/rei-flash-18-pack

Too small for backpacking, unless you are one of those bivy sack people with a matching $500 ul sleeping bag.

Yes I agree, sorry I thought people were just talking about a light pack. By that measurement, the Ikea bag is in a similar situation. It doesn't look much larger, maybe 22L?

I think its more like 30; look at the picture with the full stuff sacks. those are at least 7L stuff sacks, there are two of them, and theres room for 2 more of the same size. I backpack with a 32 liter and the interior volume looks comparable.

Is there a non-arbitrary definition of ultralight? It seems yesterday's "ultralight" is tomorrow's "lightweight" gear.

Nope, nothing non-arbitrary. By my standards, you know something is ultralight if you had to specifically seek it out. Usually the big brands that appear in outdoor stores don't make UL gear because the materials being used are too fragile and it would cause a warranty nightmare scenario. A real ultralight pack requires care, taking note of the roughness of the surface you set it down on, etc.