The Back In 5 U-lock from Ortre is a compact theft deterrent designed to keep your bike safe as you dash into the store or grab a coffee. It’s not the strongest lock and I wouldn’t use it as a primary lock in high theft areas, such as on campus, but as a secondary lock or use in low crime areas it functions fine.
Unlike most locks, this one has push-button locking, so the key doesn’t need to be in the core to lock it. Measuring 4 by 7 inches, the BI5 is just long enough to secure my front wheel to the down tube, or lock the top tube to a rack, and it’s small enough to fit in a jean pocket. It’s also light, 520-grams, so I left the BI5 in my pannier, which was perfect for when I forgot my other lock or made unplanned stops on the way home from work. BI5 is a good lock for $40 and better than no lock at all. Two keys are included and four colors are available.