The U-mount can be mounted on square surfaces. Works perfect on for instance the rollbar on a fork lift. Dual sets of AMPS holes makes the fitting of the base/top (item no. 215516/216516) easy. Comes with complete set of 4 screws, 4 lock washers and 1 Allen key for attaching base/top and 1 Allen key for locking the U-mount into place. Fits bars with a width between 25-30 mm. Color: Black.