Review on PHYHOO Bracelet Mandrel and Sizer Tool with Jewelry Mallet and Hammer - Bangle Bracelet Shaping and Size Measurement Gauge by Denise Davis

This is a good product for its purpose. Totally useless for those who need a visual representation of measurements like cm or inches. HK means nothing and neither do small numbers. It is for reference only. The big numbers are the diameter. Here's a good explanation I got from another site: The spike has two columns of numbers. The larger numbers that have the symbol at the top of the circle with a line through it refer to the inside diameter of the bracelet. For example, 13 corresponds to 56.5 in another column. 56.5mm is the inside measurement of the strap from side to side. The smaller numbers (HK) are for designation only. You don't measure anything. For example, if you have 7.06 inches in your records, which is 13 and 56.5 mm in another column, you know that 13 is your 7.06 inch bracelet. Smaller numbers aren't that important, they just help. You can ignore this column and just use the higher numbered column. PS - I found an awesome frame from Fire Mountain Gems that is listed in inches! It's definitely more expensive, but useful for those who don't need a diameter.