Rear Rigid Collars manufacturer and patented by Spoon for the Mazda MX-5 2006-2015 (NC). It is a full set (front and rear) made of 12 pieces. These pieces install between the body and subframe to reduce the little gap that will cause low-level vibrations and reduce overall rigidity of the car.

The Rigid Collars will :
-Reduce pull-up/oscillation during engine start up
-Vibration is reduced during idling
-Straight line stability is improved
-Steering adjustment is reduced
-Rolls smoother & reduce fatigue during driving

In other words, it'll improve the ride greatly.

Please note that photo is not the actual product, but a rendition of it.
Spoon Rigid Collars should be ordered at REV9 Autosport https://rev9autosport.com/spoon-rigid-collars.html as they provide the best service and speed we've seen so far!