A shock absorber comprising: a pressure tube defining a fluid chamber; a piston assembly disposed within said pressure tube , said piston assembly dividing said fluid chamber into an upper working chamber and a lower working chamber ; a piston rod projecting out of said pressure tube , said piston assembly being attached to said piston rod and said piston rod including an axial fluid passage that forms an internal bore extending through a portion of a length of said piston rod and acting as a portion of a fluid bypass flow path ; a frequency dependent valve assembly attached to said piston rod , said frequency dependent valve assembly comprising: a housing attached to said piston rod , said housing defining a fluid cavity ; a spool valve assembly disposed within said fluid cavity , said spool valve assembly including a spool valve and a bypass valve assembly, said spool valve being slidably disposed within housing , said spool valve including an axial passage being in flow communication with said axial fluid passage of said piston rod , and thus forming a portion of said fluid bypass flow path; wherein movement of said spool valve within said fluid cavity changes an amount of fluid pressure required to open said bypass valve assembly; and wherein said bypass valve assembly includes an interface and a valve disc, characterized in that said frequency dependent valve assembly further comprises a spring biasing said valve disc into engagement with said interface , a bypass chamber being defined by said interface and said valve disc . a pressure tube defining a fluid chamber; a piston assembly disposed within said pressure tube , said piston assembly dividing said fluid chamber into an upper working chamber and a lower working chamber ; a piston rod projecting out of said pressure tube , said piston assembly being attached to said piston rod and said piston rod including an axial fluid passage that forms an internal bore extending through a portion of a length of said piston rod and acting as a portion of a fluid bypass flow path ; a frequency dependent valve assembly attached to said piston rod , said frequency dependent valve assembly comprising: a housing attached to said piston rod , said housing defining a fluid cavity ; a spool valve assembly disposed within said fluid cavity , said spool valve assembly including a spool valve and a bypass valve assembly, said spool valve being slidably disposed within housing , said spool valve including an axial passage being in flow communication with said axial fluid passage of said piston rod , and thus forming a portion of said fluid bypass flow path; wherein movement of said spool valve within said fluid cavity changes an amount of fluid pressure required to open said bypass valve assembly; and wherein said bypass valve assembly includes an interface and a valve disc, characterized in that said frequency dependent valve assembly further comprises a spring biasing said valve disc into engagement with said interface , a bypass chamber being defined by said interface and said valve disc . a housing attached to said piston rod , said housing defining a fluid cavity ; a spool valve assembly disposed within said fluid cavity , said spool valve assembly including a spool valve and a bypass valve assembly, said spool valve being slidably disposed within housing , said spool valve including an axial passage being in flow communication with said axial fluid passage of said piston rod , and thus forming a portion of said fluid bypass flow path; wherein movement of said spool valve within said fluid cavity changes an amount of fluid pressure required to open said bypass valve assembly; and wherein said bypass valve assembly includes an interface and a valve disc, characterized in that said frequency dependent valve assembly further comprises a spring biasing said valve disc into engagement with said interface , a bypass chamber being defined by said interface and said valve disc . <EOS>