My TNF Base Camp 90 liter duffel bag has served me well, but most of the time I wished I had a slightly bigger and lighter duffel bag (with similar features). The Patagonia Black Hole 120 liter duffel looked like a good choice - lighter, similar features, and 30 liters of extra space. I really need that 30 liter space. I wish I could compare the bags side by side, but unfortunately that's not possible as there is no shop in my area that sells the Patagonia's duffel. I did my homework online, and came up with a weird conclusion that the two bags must actually have pretty similar volumes, and no way 30 liter difference!

Here is the math (in meter scale):

TNF Base Camp 90 l:

According to the manufacturer, the bag measures 71x41x41 cm. The volume (in liters) of such a square box (rectangular prism) is ca 119 liters. The TNF duffel is almost a perfect cylinder, so it's volume is then easy to calculate: 71 x (41/2)^2 x Pi = 93.7 liters according to the manufacturer's measurements. It makes sense, no problems here. I did check the measurements at home, and they seem to be correct.

Patagonia Black Hole 120 l:

According to the manufacturer, the bag measures 79x38x36 cm (approximately, after converting inches to cm and rounding up). The volume of such a rectangular prism is ca 108 liters. As the bag is not a rectangular prism, the true volume should always be less than 108 liters. Here I'm assuming that the manufacturer has given measurements for maximum length, width and height (otherwise, what sense do they make?!).

The conclusion is that the two duffel bags must have more or less similar volume, and not differ by 30 liters! Unless Patagonia's official published measurements are something else than I assumed them to be.

So, is the actual volume of the Patagonia Black Hole really 120 liters (any users out there?)? Really 30 liters more than the TNF Base Camp 90l?