Profile Design's J4 Bracket Kit lets you fine-tune your aero position down to the millimeter. For lightness, strength and aerodynamics, the brackets are made of forged and CNC-machined 6061 aluminum and have Marine-quality 12.9-grade bolts that are corrosion-resistant and hidden. For easy and fast adjustability, by simply loosening the fixing bolt on each side you can slide your extensions in and out. Meanwhile, the brackets hold the armrests set back 20mm from the center of the base bar or you can reverse the armrests for a forward position. You can also stack aftermarket risers on the brackets to raise the armrests (armrests, risers and extensions sold separately).