Standard rear light unit E marked. 12V type.
Not saying its a big unit but you could probably pack your lunch in it.
Tail and stop light.
Dimensions:
Width 130mm
Height 95mm
Depth 750mm
Fixing studs:
2 X M6 X 14mm X 1.00 pitch
52mm apart (centers)
8mm above middle of unit.
Wire Colours:
Green
Green/Yellow
Brown