The stretch vest is sized a bit small (I normally wear large but got the size XL) and it fits perfectly. Had minimal flapping when I get up to speed specially on the downhills and the weather is somewhere in the 50s or low 60s.
I bought this for my partner for Christmas. He usually wears a medium and occasionally a large. I ordered the large and it is definitely a race fit. It is very visible and folds up small to put in the pocket. Looks sharp but order a size up.
Used this for a ride between 32-40 deg f. I would have been miserable with out it. I do have a single issue with this, but more so because I am an odd shaped person, I have a very long torso and it isn't exactly long enough to stay down in the front. Normal people shouldn't have an issue with this
This vest is as thin as toilet paper - quite useless.