方形鋁合金環形心軸（漸進尺寸）

I was pleasantly surprised by how smooth the hard anodized aluminum feels compared to my old steel mandrel. The square shape is genius for keeping my ring shanks straight while I hammer, and the sizes 1-16 cover everything I need. This is the kind of tool that makes me actually enjoy sizing work.

Finally found a mandrel that won't rust or wear down, and the hard anodized aluminum feels solid in my hand. Sizing up to 16 is perfect for my larger custom pieces, and the square shape keeps the rings from spinning while I work.

I mainly use this for sizing up my rings to a 9, and the square shape keeps them from rolling off my bench—a huge plus. The hard anodized finish seems solid, though the size markings could be a bit easier to read at a glance.