When specifying the configuration of the SE7300 you can choose between "50" and "55" in step 5 of the part no.
Field Devices, SmartStruxure Lite
Different options of configuration when defining the part no for the SE7300
The difference is that the "50" option is PIR Ready, but PIR cover of unit is not included. Option "55" is with the PIR cover already mounted upon delivery.