Wet sleeves are part of some original engine designs. The sleeve forms part of the water jacket and is sealed at the top and bottom with gaskets or o-rings. These sleeves are robust and have the advantage of replacement as a factory finished unit. (Finished piston and sleeve assembly). They have the disadvantage of failure due to coolant loss via the o-rings to the crankcase. Corrosion of the block is common where wet sleeves are part of some alloy block designs. Close inspection of sealing areas is vital.