Part# YT6023 - Yella Terra racing roller rockers, shaft type roller set to suit Nissan Datsun 4 cylinder A series engines. A10, A12 & A15. The ultimate race set up, proven over many years is this race series roller rocker gives you valve lash adjustment and minimal reciprocating weight in the strongest rocker arms available. Direct bolts on with no machining required ~ For use with mechanical or hydraulic camshafts. rocker arm ratio of 1.55 : 1, includes shafts and mounting pedestals.