I have the $159 variety. I guess it works. I don't know how I would know if it is accurate or not.

Loosen the strap screw all the way and pull the strap taught before using the tension screw to make it tight on the barrel. Read the directions prior to using the thing.

On a remmy Varmint I had to use the larger of the 2 supplied spacers. On a Savage 12 LRP, I used the smaller of the 2 provided spacers.
Getting it to work consistently took a few tries with the bayonet at different locations, so don't get frustrated.