Luxuglow 4 Pcs Double Cut Rotary Burr Set 1/4 Shank 6mm Tungsten Carbide Rotary Cutting Burr Long Reach Rotary Burr Bit Grinder Drill File Cutting Burs for Grinder Drill, Metal Polishing,Engraving

EDIT: Since writing this review the first time I've purchased 2 more sets of these. They may wear out but it's still way more economical to buy these than anything else I can find.These really do not work well for porting cast iron heads with a pneumatic die grinder. The cutting heads seem to be brazed on or something and a significant portion of the cutting burrs fractured off immediately upon contact with the cast iron. I was barely able to remove the thermoreactor hump on 4 bbf exhaust ports before these tools left such a rough surface finish that I had to stop. Also the shaft is so long, relatively unbalanced, and flexible that at speed that the end of the tool spins off center causing vibration and bouncing bouncing.That being said, these things remove a solid amount of material. You could really mess up some aluminum heads with these if you wanted to. For the price, I did get what I was expecting. Slightly better than the harbor freight dremmel attachments.

I recommend using this product for sculpture, and engine head porting (Iron and Aluminum) ِvery good, High quality & good packing and excellent shipping.

Burrs quickly become dull and useless within 10 minutes of use on aluminum.

Works well