Sometimes you just need to measure the diameter of someone's thumb, finger, or toe - and account for the size of a knuckle.  These ring stars cover all diameters from 10 mm to 29 mm.

Attempt to slip a ring over the individual's finger, thumb or toe - up to or past a selected knuckle.  If the ring is too small, rotate the star counter clockwise and try again.  If the ring is too large... well, you get the point.  When you fine a ring size that fits just right, add the number in the center of the star to the number at the base of each branch.  That total is the diameter of the best ring in millimeters.

The stars come in two thicknesses - 3 mm and 10 mm. The 3 mm rings are most appropriate if your hand is typically contracted. In that event you'll need a thinner ring as you turn corners and pass over your knuckles. The 10 mm rings are most appropriate if your hand is typically extended. A 10 mm ring will come closer to matching the device that you'll end up putting on your fingers and will better represent the stability that a thicker ring will provide and the amount of friction that the additional surface area will impose as you try to slip it on and off your finger.

You can learn more about these measuring rings - by going here: https://wp.me/P9evBA-hR