I have a Topeak MTX also and like it a lot. The mount system is great, more solid and easier to secure than the velcro straps on the cheaper bags. There are three different bag sizes and a few different racks in the series. I have a solid rack on my cross check and a seatpost rack for my mountain bike so I can use the bag on either bike. I tried a less expensive rack trunk from Performance and it didn't work well for me. It was a pain to take on and off and wasn't stiff enough for my uses.