The Ring Sizer Mandrel is made of high-quality aluminum alloy, to measure rings sizes. There are 4 types of measure sizes stick on it: American size 2-15 (US ), Hong Kong size (HK), Japanese size (m/m ∮), European size (CU). The front and back sticker sides are designed in flat for easier reading size, and both sides are graduated rolling and non-slip grooved design is to keep rings in level when measuring.