MDR Industries | Billet Coolant Expansion Tank | Honda Civic Type R | FK8/FL5 2.0T K20C1 | 2017+MDR's direct replacement upgrade billet expansion is CNC machined out of 6061 T6 aluminium alloy, TIG welded, and anodized. This was created to address the issue of leaks at the seams from the factory plastic expansion tank cracking due to continuous heat and pressure cycling. This billet expansion tank is a direct factory replacement. Size and shape are identical to the factory plastic unit while utilizing all factory mounting location and hoses.