This is Knobbles and Bobbles' classic blue ceramic knob, the diameter of this knob is 3.5cm and the bolt will fit through a door that is up to 2.5cm thick.
Longer bolts are available from the menu under All Knobs -> Fittings and Longer Bolts.
Each knob is supplied with the ceramic head and metal fixings including bolts and washers. Any questions? Please ring us on 07746 357625.