Under Axle Bar Mount, 3 in thru 3-3/8 in Axle, U-Bolts DownUsed with U Bolt down configuration, will have the U Bolt nuts at the bottom, under the axle. Works on most trucks with 2. 5" or 3" wide leaf springs. For all axle tube diameters between 3" and 3 3 8". For use in conjunction with our standard traction bars. This kit does not come with any hardware, because hardware is included in the pivot mount frame kits.