ST4P3SM5 - 

Tyco Electronics now offers several of their popular SCHRACK plug-in relays in “packages”. Each package includes a relay, socket and hold down. Some also include accessories such as protection circuits, LEDs and marking tags. This simplifies ordering and helps prevent situations where the wrong socket might be ordered for a given relay or where quantities of the various components do not correspond.
Packages are available for SNR, XT, PT and RT series relays. They find application on DIN rails in control panels in industrial machinery, alternative energy systems, elevators and other commercial equipment.

Features:

Several Components Can Be Ordered Under One Part Number

Quicker and Simpler Than Having to Assemble Components

Packages Can Simply Be Snapped Onto DIN Rail

Prevents Situations Where the Wrong Socket Might Be Ordered