Its a mix of custom ram for some builds or modified rams. You will find higher end bots such as beta will have custom made rams.
For those with lower budgets, its easier to modify an existing ram. I have some festo rams and im just swapping the top cap and shaft on mine, but i have also machined ram parts for feather builds - i do custom cnc machining for quite a few roboteers.
One example is the feather diotior, that had a custom ram setup. You can see the PTFE? block in the images above, its that cream thing on top of the piston. It may be nylon? not sure till i sort my test one out!

Shooty is correct, there is a 2nd ram which operates at a lower pressure to fire the ram down. it means less f a good hit in the reverse, but less air is used to retract meaning you have more for that big blow.