The MAXX Series is taking the affordable performance cylinder head to the next level. There is no comparison in the market. Our new ultra smooth casting made of Grade A 356-T6 aluminum is precision CNC machined to create the perfect platform for our new runner and chamber designs. This combined with our 5 angle competition valve job, diamond honed bronze guides, hand bowl blending and assembly by our professional builders right here in the U.S.A produces out of box performance that out performs the top brands in the industry. MAXX quality & MAXX performance at minimum pricing – Promaxx Performance.