Honda D15-16 Block Guard ALL SPEC PERFORMANCE 1813001 Our block guards are custom designed and CNCed out of 6061 aluminum They are slightly over-sized to compensate for the cylinder walk flaw (so common in open-block designs), and to ensure a water tight seal around each cylinder when pressed in your block It also features a beautiful orange anodized finish for better corrosion resistance; additionally, our block guards have machined pores for better cooling To top it all, they are made right here in the USA