Most race car brake cooling air ducts are made of silicone and rated to at most 20psi (125kPa). Brake cooling ducts are powered primarily through ram air effect, and cost a few bucks a foot.

Not sure what OP is referring to, but if they're talking about a replacement to the 10-12cm high-temp diameter silicone air hose that typically gets routed to just front of brake rotors (and rated to 230C sustained, 260C intermittent), those measurements are MUCH higher than anything I've seen on genuine, real race cars, including WEC prototypes.

Now, the initial ducting may be made of a composite (including carbon fiber), which obviously can be tremendously strong, but the last bit of it is usually silicone.