Elise rear lights (older incandescent or LED doesn't make a difference) are 120mm outer diameter and the bolt holes (M5) are pretty much 100mm apart.
Only the later Elise models (S3) and Evora now use 2 sizes with the outers the 120mm round ones and the inners being a small type for reverse light and such.
Don't know what the diameter of the small ones are.
Bye, Arno.
Thanks Arno, much appreciated!