Profile Design 39a Aluminium Aerobar ExtensionsOverview The new range of extensions have evolved from our well proven T Series. They have been designed to offer distinct fit options. We have also adopted a new naming system whereby the name gives the angle and material of the extension. Thus 39a is a 39 bend in aluminum. Performance The sole purpose of extensions is to provide a comfortable position for the riders hands relative to the armrests. They enhance performance by allowing the rider to