The Riva high-quality ductile iron replacement sleeves are considerably harder and more abrasion resistant than OEM sleeves providing excellent oil retention, ring seal and the ultimate in leak down performance. Sleeves lock firmly into place during installation against machined step in engine block preventing possible dropping or shifting, protecting head gasket seal. Accepts pistons for stock bore (86mm) up to 87mm (2nd Over RIVA Pro-Series Pistons). Sold individually.