A set of new old stock standard size pistons to suit the Rover P5 3 Litre Mk3 . They have the part number 536270 , designed specifically to suit engines with an 8 to 1 compression ratio . The pistons are termed Grade C , not sure what that refers to . They come with gudgeon pins and rings , the rings packaged separately . I have inspected the rings and found that one ring each packet has some corrosion,  the corrosion appears confined to small areas on the upper surface of the ring , the sealing surface looks OK .