This stuff has been around for a while, but a bit hard to get.
It's a 60 grain bullet in a 22 short case, with a tiny pinch of powder.
I have been interested in it, but I heard that you need a 9" twist barrel... which I didn't have.
I saw that Midway carried it, so I bought two boxes and tried them in my 40XB rimfire rifle and they are great. They fly at 850fps, and you can watch them fly down the range if the light is right.
My rifle has a 14" twist.
They are accurate enough to hit 2" rocks at 100 yds.