Description THIS IS A WELD ON SPRING SOLO SEAT MOUNT. IT IS MADE OF 1018 MILD STEEL, FOR EASY WELDING. You may need this to complete you custom bobber seat installation. THE MOUNT IS 1 1/8" IN DIAMETER, AND THE STUD IS 3/8" IN DIAMETER. THE STUD HAS A 1/8TH" COTTER PIN HOLE, TO SECURE THE SPRING IN PLACE. Free shipping if purchased with a seat. If you have any questions, call 314-392-7841.