In short, a qualified professional bicycle mechanic. For the longer version, have a read through ‘The Inception of Abu Bicycles’ from the blogs. https://abubicycles.wordpress.com/2017/02/24/the-inception-of-abu-bicycles/ Also check out the following social media platforms: http://www.facebook.com/abubicycles http://www.facebook.com/hajjride http://www.instagram.com/abubicycles/