The bottom nut, that holds the strut together when the spring is compressed, is a lower profile nut. If, a "Nyloc Nut", the one holding the retainer to the strut tower, is used in the lower position, the rubber ringed retainers center portion, will bottom out on the taller profile nut before the retainers rubber portion touches the tower, as viewed from the top. I made this mistake the first time I did my struts.
