These glass cabinet knobs have been recovered from the overstock of Emery&Cie, a Belgian tiles manufacturer specialised in Zellige mosaic tilework. According to the manufacturer, these cast glass pieces were manufactured in India in relatively primitive kilns, which gives them that imperfect and irregular appearance. The front is round and the back has a flat top. 

New, from an overstock (never installed). May have some light chips or some imperfections due to storage. There are some tiny internal cracks, which are a natural feature of these handcrafted glass pieces. The shade may slighlty vary from one knob to another. A bit dusty, needs to be cleaned. 

More info here