This listing is for a set of (8) 4.390" Bore Size Speed Pro Hypereutectic Pistons and Matching Hastings Piston rings set compatible replacements for 1966-69 Chevy 427 cubic inch big block 335HP & 390HP closed chamber heads. Domed head .140" high. DurOshield skirt coated piston. Approx. Compression (w/.030" bore). 5/64" 5/64" 3/16" ring grooves, Stock 6.135" length rods Press-fit only Stock 3.766" stroke Pin diameter: .989" (included) w/106.9cc chambers 9.46:1 w/116.9cc 8.73:1 Stock 6.135" length rods Press-fit only Stock 3.766" stroke