I decided to add a rack to my Series 500 ST, and I ordered the Ibera that Ride1Up recommended from Amazon, but it did not fit and I had to return it. If it could be adapted somehow, I could not figure it out. I see that R!U has changed their recommendations somewhat. They still recommend the Ibera but they also recommend this one Songmics. Anyone have any experience with these racks, or can you recommend another one that will work with this bike? Thanks.