This is a rear subframe reinforcement brace made by HARDRACE.
The brace reduces flex and sag in the vehicle's chassis, making the car stiffer and improving handling response under high speed driving and hard cornering.
It is introduced on Ameblo's "M&M HONDA's Honda Honki."
https://ameblo.jp/mandm-honda/entry-12808172050.html?frm=theme
