I have used many different shields. I agree with the drawing that the best shape is the curved one on the right.
I make mine out of old window blinds. I think the last one I bought at a cheaper than dirt for about 5 bucks. Had enough panels to make 20 mirage shields
Ron, thanks for sharing, neat idea. Get a package of two-sided, sticky backed, velcro and make your own. Al, just one more variable eliminated. This barrel mirage is definitely a condition that all good shooters should be aware of. Anyone care to share their experience and cure for this. Thanks, WWE