What's the difference between CUCM-USR-LIC and R-CUCM-USR-LIC?

[jbinostrozam]

I'm following CUCM 8.6 ordering guide and it recommend Top level part number R-CUCM-USR-LIC instead of CUCM-USR-LIC?

What's the difference?

[skilambi]

One is E delivery and other is paper media. R means E delivery which would be recommended.

Thanks

Srini