The Sonic bracket offers an extensive fit range, low weight and easy adjustment along with minimal frontal area. Combining this with the Ergo armrest creates an aerobar that will aid most riders in optimising their position for both speed and comfort. The 39A is one of the newest versions of our reliable aluminium extension range. Performance The Sonic/Ergo is designed to present minimal frontal area to create as little aerodynamic drag as possible. The main purpose of an aerobar is, of course, to get the rider into a fast position despite a fairly minimalist appearance the Sonic/Ergo offers a comprehensive fit range for exactly this purpose. Fit Data The 39a extensions have a 39° for the grip . The rider can choose whether to hold high for the shrugged position or low for a more open, head up position. The extension length and rotation can be easily adjusted using the top bolt. There are 100 distinct position options achievable just by moving the armrests. Combine that with the risers and this bar offers 1500 possible configurations. As a clip on bar it is also possible to adjust the extension width and tilt easily. This is the most adjustable clip on bar on the market (and in history). Armrest Offset: -70mm to -17.5mm in 7.5mm steps Armrest Width: 124mm to 290mm in 18.5mm steps (With Extensions at 100mm) Armrest Stack: 60mm (no riser kit) to 130mm in 5mm increments (With aftermarket Riser Kit) It is worth noting that our previous top level clip on aerobar, the J4/F35, offered 90 possible configurations. This highlights the significant step forward we've made with our new generation aerobars in allowing riders to precisely adjust their position.