0.027" thick Copper Disc - what are they used for?

[Icarus]

The title says it all.

0.030" copper discs are used to shim Seoul emitters to put them at the right focal height but I'm wondering what the 0.027" discs are used for? :thinking:

Thanks.

 

[Probedude]

solder layer?

 

[Norm]

Used when replacing a Luxeon LED to bring the Seoul up to the right hight for proper focus without trimming 0.030" off the bottom of the reflector.
Norm