This is Knobbles and Bobbles' interesting etched ceramic knob, the diameter of this knob is 3.8cm and the bolt will fit through a door that is up to 2.5cm thick.
Longer bolts are available from the top menu under All Knobs -> Fittings and Longer Bolts.
Fitting instructions can be found on our FAQ page.
Please let us know if you have any questions.
Info@knobblesandbobbles.com or 07746 357625.