This is Knobbles and Bobbles' pretty patterned white 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.
Each knob is supplied with the ceramic head and metal fixings including bolts and washers.
Please contact us with any questions. Info@knobblesandbobbles.com or 07746 357625.