One of the charges often made against wet liners is the difficulty of ensuring a perfect seal between liner and cylinder block. It is vital that sealing rings should effectively prevent leakage of coolant into the crankcase, prevent lubricating oil entering the coolant circuit and avoid distortion of the cylinder liner. The author maintained that there are no difficulties when the design is correct and the right type of seals are used. There are three basic types of wet liner in general use as illustrated in Fig. 1. Types X and Y are sealed at the top by compression of the flange while the lower end is sealed by rubber rings. This paper deals with these types of seal only.