This is a top tube bag from Montbell. I believe it's sold under the name "Frame Pouch." The maximum dimensions are 4cm wide, 20cm long, and 32cm across. I tried this bag, which attaches under the frame, because I was concerned about the appearance of the Topeak bag I'm also selling, which attaches on top of the frame. However, I ended up rarely using it, so I've been storing it.