We choose Dynapro calipers over the more common and cheaper Dynalites because they're stiffer. But you can make them even better with a bridge bolt - they make the caliper approximately 10% stiffer.
You need to remove it in order to change pads, but it reinforces the weakest part of the caliper and increases the rigidity. This means better pedal feel with less flex and more precise threshold braking.
Fits the four-piston Dynapro as used on our NA/NB Big Brake kit, NC Little Big Brake Kit and ND Big Brake Kit. Not required on the 6-piston Big Mama Jama kits.
Kit includes two bolts, which is enough for two calipers. Since we never install more than two Dynapros on the same Miata, that's enough for one Miata.