I purchased the modular 4 with the intention of taking my Subaru outback back from my 2 and 5 year old. I can use one bag for their stuff, one bag for my stuff, emergency gear, etc. I also purchased 2 of the cooler bags that fit this system b/c we live a little outside town and it's nice to have coolers when we go food shopping in the summer (among other things coolers are great for). I have the 2 cooler bags and 2 of the regular bags in the Modular now. The whole system is a little bigger that I anticipated (yes, I read the size chart), but it's better to have a little more space than less. A nice option would have been to be able to choose the bags that go along with the system...for example if you purchase the Mod 4, having the option to do all 4 bags (like the current system) or 3 bags and a cooler, 2 bags and 2 coolers...etc. Even if it costs a little extra for the cooler bags. With my current system, I have 2 extra bags that I am not really using.
Nice material, well made, overall happy with my purchase!