After you decide to get the Topeak rack for your bicycle you will then need to decide what trunk bag to get in order to complete your storage system. While most people typically choose just one trunk bag from the many options available, keep in mind you may choose to buy multiple bags in order to have different options on different days. One of the most popular selections is the Topeak MTX trunk bag because it is a reasonable size and also less expensive than the bigger bags. Matt from TailHappyTV decided to get the Topeak MTX trunk bag instead of the larger DXP or DX versions of this bicycle rear rack bag. You can watch the video he posted to learn a lot more about the features of the Topeak MTX trunk bag and which rear rack you should get for your bicycle if you decide to go this route.
If you have a bit more money to invest in your bike bag you may want to consider buying the larger DXP version or get one with saddle bags as well. As long as you don't mind the extra weight and cost you'll be able to transport more stuff with you on longer bike rides. Like I mentioned before, you can get both a small bag and a larger bag to swap out based on the needs of your particular ride that day. Another thing to keep in mind is a waterproof version of the Topeak trunk bag if you live in a very rainy climate. Alternatively, you could just get a rain cover for you Topeak MTX trunk bag if you decided it's not worth it to invest in a waterproof rear rack bag.