This listing is for a Pioneer Stereo Receiver Knob part number AAB-099. It is correct for the Bass, Treble and Balance Controls on SX-450, SX-550, SX-650 and SX-750 models. The outer diameter is 18 mm.
It is in nice condition, but used, so it can use a cleaning and under close scrutiny minor imperfections consistent with normal use can be expected.
If the buyer address is outside of the U.S. the customs and shipping will be handled by eBay's Global Shipping Program. I have no control over that service or what they might charge. I have heard it can be expensive.