This part connects the left and right struts using a high-rigidity aluminum oval bar, definitely increasing the rigidity of the rear. This is a standard strut tower bar for body tuning. It compensates for the twisting and lack of rigidity of the rear, and maximizes the directness of the steering and the grip of the tires. Installation is a simple task of just joining the left and right struts with the tower bar.
It is introduced on Ameblo's "M&M HONDA's Honda Honki."
https://ameblo.jp/mandm-honda/entry-11825504234.html