Customizable Black ceramic ring core 

4mm total width, Approx. 2.4 mm thick 

6mm total width, Approx. 2.4 mm thick 

Flat top with no inlay groove, perfect for ring makers wanting to customize the channel to any requirement or wanting to engrave the rings with pictures.

No need to make the core from scratch, all that's required is a channel and a little finishing afterwards and these become custom cores.  

Black Ceramic, sizes 4-15 available