Background: I commute to work several days a week and I have storage needs that include rain gear, an accordian type of binder for work stuff, a pair of dress shoes, a hanger (for my leathers), and space for lunch. I put all of this stuff in a tail bag and use a tank bag as well, mainly to have a place to put my ipod and put food if I go through a drive thru. I used to use a Tour Master Deluxe Tail Bag, which I like, and a Cargo Tank Bag, which I did not have any problems with. The two together met my needs; however, what I did not like was having to hold my tail bag, tank bag, and helmet when going into a building.
What I wanted was a tank bag that would zip into or attach to a tank bag so that I wasn't juggling so many things. With this in mind, I gave the River Road Tank Bag System a try (Bike Bandit has it on sale for half price).
River Road Tank Bag System w/ Magnetic Mounting Base at BikeBandit.com With this tank bag, you get two bags that zip into a base or each other. What I have done is zip the small bag into the base on the tank and use the big bag as a tail bag as it has loops that you can run bungee cords through. Although the larger bag is smaller than the Tour Master Tail bag, the smaller bag is bigger than my old Cargo tank bag and so it kind of balances out so that I can keep everything I used to carry with me still. The only problem I forsee is that with the Tour Master Tail Bag, I had enough space to stuff my synthetic down jacket during the winter, but with the River Road setup, I'll have to stash it on some webbing on the outside of the bag.
What I love about it is that the small bag zips onto the big bag, and the big bag has backpack straps. What results is a huge backpack that looks ridiculous, but allows me to have my hands free to carry just my helmet. It does take an extra bit of time unzipping the tank bag from the base to the large bag and to put it back on the base, but it is well worth it for me. Note: it does not come with bungee cords (I use the Tour Master cords), and it only comes with one rain cover (I use my Cargo rain cover for the small bag and use the one that came with it on the large bag). I'm not sure how durable it will be, but I love the concept so far.