The knuckle is the fullest part of a finger. A ring should slide over the knuckle snugly but without tearing into the skin. The difference in circumference of a knuckle and proximal phalanx varies from person to person. Unless your engagement ring is elastic, you have to live with the ring-spinning freely on your finger. It is a typical problem without a perfect solution. Adding traction inserts, such as balls, bars, bullets, shots, or liners inside the shank will reduce spinning and make it feel closer to the skin. An innerspring can also be added to hug the finger once the ring has cleared the knuckle. There are also prosthetic shanks that open and close, such as FingerMate or SureFit. They have limited use because of the high cost and short life span. In addition, prosthetic shanks have a concealed movement making them bulky and incomparable with high-end, delicate jewelry. We account for seasonal or even daily changes when measuring a finger because the size varies with weather, diet, or medical conditions. Air temperature, humidity, atmospheric pressure, seasonal changes (up in summer, down in winter), hours (up in the morning, down at night), childbirth, and feminine cycle all affect the size, sometimes severely. Each measurement is a snapshot of the size on this day, at this time, etc. Therefore, we need to know how your personal size fluctuates to ensure a proper fit.