This brass reamer is designed to not only flare openings, but is the correct 1:10 taper and size for making 10mm Female Joints. With a balanced counterweighted handle, this reamer is very comfortable to hold and tool with. The fine tip and thin overall length of this reamer allows for you to work in tight spaces and openings in your glass. Built with Prime quality brass for durability, this tool should last you for years. Look for this reamer at a discount in the Prime Brass Trinity kit, which includes all 3 of these great tools at great deal!