There are a number of commercial products based on Red Hat Enterprise Linux (RHEL). Information about these products and the version of RHEL they are based on is often difficult to come by, since this fact is not widely publicised. Sometimes it is possible to run the 'uname -r' command to see the kernel release and then cross-reference in the version history section of the RHEL page.
Examples
Check Point SecurePlatform VSX R67 is based on Red Hat Enterprise Linux 5.2. [4]
References
Commercial products based on Red Hat Enterprise Linux Wikipedia(Text) CC BY-SA