Product information updated on 2021-08-25, Manufactured by DJM Suspension - Part Number DJM:CA2599L4, 1999-06 Chevy 1500 Lower control arm set, 4 inch drop, Priced As Pair - Medium Install - Instructions - Yes, Control arms or “A” arms or maybe “wishbones” are the components that attach the spindle/brake assembly to the frame. In almost every case there is an upper and lower arm. The lower arm is the big one, supporting the weight of the front end through a spring or torsion bar. The lower arm is where the actual lowering takes place in CALMAX systems. This is done by moving the spring perch down and lower ball joint (which attaches in the spindle) up relative to each other and the frame. Upper control arms attach to the spindle through the upper ball joint (in the spindle) and to the frame through shaft or pivot points. Upper arms have no influence on ride height but has a great deal of influence on alignment. Lowering and Alignment Upper control arms biggest responsibility is alignment, its primary function outside of the physical connection of the suspension to the frame. Typically the upper arm can be moved in and out relative to the frame and affect the camber and caster settings of the front end. These are very important characteristics regarding alignment. The ability to manipulate camber/caster and fix a “new ball joint angle” makes it possible for CALMAX systems to drop trucks so low and still be able to align to factory specs. The lower arm on some trucks (F150) have a slight bit of alignment adjustment available, but that job is almost single-handedly done by upper control arms. The original equipment control arms are typically stamped steel parts with rubber pivots. Some of the newest trucks are sporting cast aluminum arms with rubber pivots. DJM’s CALMAX control arms are all made from seamless DOM tubing, featuring urethane pivot bushings with DJM’s exclusive “twin tube sleeves”. Urethane is a smart material for making bushings. It’s heat resistant, weather proof, and most importantly is very hard and will not deflect or “squish” when loaded. Rubber tends to “squish” or move during hard cornering or braking which causes your control arms to actually move or wander a bit, throwing off alignment and upsetting handling. Urethane stays rock hard so your front end isn’t moving around on your while your driving. It does have a dark side though – It can squeak to high heaven if pinched or over tightened (especially if not lubricated). That where“twin tube” sleeves come in, two nested pivot sleeves, the innermost is slightly longer than its mate so when you tighten up the pivot point during installation your don’t “over tighten” and squeeze the urethane. Of course using a good weatherproof grease is also a must and twin tube sleeves help to insure a nice quiet and compliant drive. The tubular design of the CALMAX arms set them apart from other methods of lowering and provides style to your suspension. Often you do not have to change coil springs to get the radical drop you are looking for, sticking with the factory spring you don’t loose any travel or have a radical change of spring rate. An attribute only Calmax Control Arms can claim.