998cc dished circlip type piston with 4 rings. Compression range of 8.3 to 9:1 depending on block and head but for best performance use later 3 ring flat top piston
ADU3490-60. If you want to go faster, keeping that 998cc block, Big bore is the best answer; boring to over 1000cc will yield a very noticable improvement! Sold singly,4 per engine required