...Avantgarde....they, the x51 photo of yours....look JUST like the OE on my 997 C2.....now replaced with EvoMs ...which look just like the FabSpeed image our friend jhbrenna showed us. By the way the other headers he shows, from the Fabspeed site, are NOT 997 design (c2or 4 it is claimed)--they are 996---

Cheers

KiwiCanuck