Yes the std puma shocks are gas charged, an improvement on the td5 model. I have recently fitted a set to an earlier defender, a great improvement on the std non gas unit. The only puma ones I have ever needed to replace have either been damaged by rocks etc, or when upgrading for severe service to koni raid 90's .
Currently having great results with The Ultimate Suspension shocks, closest to the decarbon inperformance that I have found, and at a way better price, they can be valved to suit your specific application, too.

Jc