The bullet belts do not have firing pins or gun powder in them and are fashion accessories, so they will safely pass through customs. We have never had a problem with customs detaining any of our bullet belts.
The sizing is in inches. So, if you have a 34 inch waist you would probably want to go up to a 38 inch belt. Each of the bulletslinks are removable so you can adjust the belt to any length you would like.