New, never installed, Valvetronic Designs BMW M3/M4 G80/G82 Exhaust Channel Brace. Required for ANY high-performance aftermarket exhaust midpipe -- the stock OEM brace will not clear aftermarket midpipes.
Identical to this item (minus the logo), I had it custom made:
https://valvetronic.com/products/bmw-g8x-extended-chassis-brace