Heavy duty control arms are made with 1-1/4" DOM tubing and 1" DOM cross bracing. Flat bottom design works with 5" or 5-1/2" conventional springs which must be mounted with the closed end seated in the control arm and the open end in the upper spring cup or a spring ramp (sold separately) may be welded onto the lower plate to place the open end down. Black powder coated arms feature high quality rod ends and separate shock bracket which will require welding or bolting onto arm. Rod end spacer kit is required to adapt rod end to fit in the stock frame mount (sold separately). These lower control arms are intended for racing and will not accept stock style lower ball joints. These lower control arms are intended for racing and will not accept stock style lower ball joints. Note: Ball joints should be tack welded into lower control arm after assembly.