I can't believe I couldn't find this model already posted.  Created this for my son who loves his hat, but can't quite get it to fit his head.  

2 clasp width sizes (based on 2 random hats I had to work with) one for child sized clasps (15.25mm), one for adult (19.7mm).

Each width has 2 different lengths posted - one with 5 nubs/holes, one with 10 nubs/holes.

I printed with 0.4mm Nozzle at 0.1mm Layer height in PETG, but I'm sure other settings and materials would be fine.