Description: Phenomenal for smoothing a stone. These will take a stone from rough grind scratches to ready pre-polish all in the same go. They work best on silicates such as agate, quartz and nephrite. The only group it is not as effective on is feldspar.
The rubber creates significant heat. This is totally fine so long as you work under a water drip the entire time. DO NOT dunk the hot stone in a water basin, it will shock the stone. DO NOT run these dry, they will heat the stone rapidly.
These have significant longevity when it comes to sanding the gemstone. even on hard agates, they will last a half dozen stones or more each. The knife edge is fantastic for V and U shapes grooves. It removes material and smooths at the same time. Black is the Coarse Grit and this is best to use after your initial diamond grinding with any standard diamond burr under 150grit. 
Please note the binder is rubber, and not silicon. these are different than the common ones that are used on metal. They look identical to most people, but these are effective on both metal and stone. silicon is not effective on stone.

Made In: China

Diameter: 22mm
Thickness(Thickest part): 3mm
Weight: 1.6g

Material: Rubber binder with unknown abrasive bound inside

Quantity: Pack of 5 Knife edge wheels. Mandrels required and sold separately.