Coaxial and Twinaxial Suffixes

What does the suffix R, G, U, A, B, and C call out when looking at coaxial and twinaxial cables?

R = Radio Frequency
G = Government
U = Universal Specification
A = Revision Level
B = Revision Level
C = Revision Level

Letters that appear before the /U characters (i.e. A, B or C) means a specification modification or revision. For instance, it is common in the CB radio industry to see the designation RG-58A/U. The original RG-58/U coaxial cable had a solid enter conduct. The “A” modification replaced the solid center conductor with a more flexible stranded center conductor (that is highly recommended for use in mobile installations). See link listed below for more details.
L-com Cable Tutorial: What is Coaxial Cable and How Is It Used?