Mi Band 2 Wrist Strap Lock Ring

Because the Mi Band 2 strap gets loose after a few month and I already lost the band several times (luckily found it again every time) I had the idea to design this useful thing as my first (and very easy) 3D object to print ;-)
I don't know if it fits a Mi Band 1/1s strap. Inner measurements used are 15.5/6.5 mm

--- Update 8.1.2018 ---

Since the first version may scratch you arm, I designed a new slim version to print with flexible filament (TPU). Now It isn't noticeable anymore.