These Amana countersinks come in a variety of sizes and the carbide bits are long lasting. After drilling thousands of holes, I broke the drill bit on a #10 countersink. When I looked for a replacement, I found the part number (630-266) on the Amana website but was unable to purchase it. Looking around I found the same part number on routerbitworld.com for about $2.50 each with $1 shipping so I ordered several. Sometimes a drill can break, so it makes sense to have a spare drill on hand. I broke mine trying to move to the next hole before getting the drill fully out of the last hole and the drill doesn't like lateral force. So these countersinks are quite expensive but last so long that I consider them good value for money. By the way, if you haven't discovered rounderbitworld yet, check them out. This is a great company with fast delivery and a great range of cutters.