The Leviton Surge Receptacles (Cat. # 5380, 7380, 8380) are designed to protect a downstream load.   During the installation and use of it is recommended that the distance between the protected load and the surge receptacle be kept to a minimum.   The surge receptacle performs best when the lead length from the receptacle to the point of use device is kept within the range of 10 ft or less.  If the distance is longer than 10 ft surge protection will be provided but the effectiveness could be diminished.   In certain conditions, if the receptacle experiences a large surge the clamping voltage will increase proportional to the length of wire between the receptacle and the point of use device.