dumb RKL question

[jaylensdad06]

maybe my google search skills need refining but I cant for the life of me find what the difference is between the PC4 and the PB4. can n e 1 shine a light on the subject for me please.

 

[MJNTWise]

http://www.digitalaquatics.com/saltwater/modules/pc4/
http://www.digitalaquatics.com/saltwater/modules/pb4/

 

[jaylensdad06]

Awsome....thanx