Look for ANSI Class Rating on the vest. The higher the Class rating the better and more reflective stuff there will be on it. My company requires a Class 2 minimum for most of our jobsites. So they buy them and I wear them

+1 on the spares, I got a case of the basic green with silver reflective stripes to hand out. I still see some of the ones I have given out along the roads near my home.
Aaron