HOW TO FIT A CUFF
Below is a You Tube link that has valuable information on how to put a cuff on properly.So please copy/paste that & check it out.. I also suggest you read what I wrote below as well,since I also cover things that they do not cover..

https://youtu.be/bU6QwykAo7w

The best way to get a good fit is to measure a cuff bracelet you already have that fits you well. The total inside circumference is the inside circumference of the bracelet from end to end plus the gap (the distance between the ends)If you don't have a cuff bracelet , then measure your wrist where you want to wear the bracelet. Cut a strip of paper approximately 8" long and as wide as the bracelet you would like to wear. Wrap the paper around your wrist where you would wear the bracelet. You might secure the paper with a piece of tape to get a better feel of the fit. Remove the paper and measure from the end to the mark for the circumference of your wrist.

EXAMPLE: If the inside Circumference end to end is 5" and the Gap is 1", the total inside Circumference would be 6" and would be suitable for a wrist approximately 5 3/4" to 6 1/4" depending on how tight or loose you like to wear your bracelets..Remember the interior does not change,but the gap can be adjusted,either by yourself or your jeweler,depending on the thickness of the gauge.

****The thickness of the fleshy part (above your wrist) is equally as important as to whether a cuff fits properly & even though the cuff could fit your wrist,if the gap is too small or too large, can make a huge difference in the cuff fitting*****

A cuff should not 'roll' around on your wrist(Too loose),nor should you see flesh hanging over the edge(Too tight) Always put the cuff on above the wrist bone where it is fleshy,then bring it down to wrist.And NEVER "squeeze" to tighten!! You will lose the integrity of the metal & if there are stones,they can loosen..Rather,turn your wrist over,push down on one end at the terminal,push down on the other at the terminal..Go easy,if the gauge is lighter.Adjusting can be done either by yourself or your jeweler,depending on the thickness of the gauge.