This is a simple variant of a locking bracelet I designed for the Engineer's Day Open House, February 28, 2015, at the University of Kentucky. The version handed-out from my lab had the UK logo on it, this one has the words "3D PRINT STRONG" on it... and strong it is! Despite printing in PLA just 2 layers thick, the tiny interlocked-3/4-circles can hold scary weights without unclasping: note the photo with the fish scale confirming it doesn't even come close to unclasping at 21 pounds of load.
This is a very easy print, spiralized in 0.25mm PLA on a MakerGear M2, except for the fact that it might not like to stay attached to the bed. Printing it with a 3-strand brim helped a lot; it takes about 5 minutes to print and uses about 3g of PLA.
This is a one-size-fits-most bracelet, so resizing shouldn't be needed.
The first photo is just the 3D PRINT STRONG version in white. The second shows both the original UK version and this version. The third was a load test of a slightly bad print of the UK version -- even the bad print was able to withstand huge loads. I put the bracelet on a piece of wire rack, and even with my fish scale's hook creasing the bracelet, I couldn't break the clasp mechanism open. The photo shows the scale at just 21 pounds because I took the photo while pulling down on the scale, which is harder than it sounds. ;-)
Incidentally, to unclasp: push the sides of the bracelet in a little and the rings will unhook. Easy.