This is Knobbles and Bobbles' bright blue glass knob, the diameter of this knob is 3.8cm and the bolt will fit through a door that is up to 2.5cm thick. If you have different requirements, please contact us as we do have longer bolts available for some of our designs. Each knob is supplied with the glass head and metal fixings including bolts and washers. Any questions? Please ring us on 07746 357625.