For SBC Chevy Tight-Fit Block Hugger Headers, Black Coated, 2.50 The block hugger headers are a favorite for street rods, as well as many 1950's and 1960's cars and vintage trucks. Most tight fit header applications require the use of Accel shorty spark plugsCompact design Will NOT fit angle plug heads1-5/8 Flange Thickness: 0.212