The shocks on a more high-end hobby-grade RC often have replaceable parts including the internal parts of the shocks (dampeners) and occasionally need the oil inside replaced or topped off. The shocks or dampeners themselves alone are composed of many pieces and are a lot tougher and are made of colorful anodized metal or a high grade ABS plastic. The oil that is used inside the shocks is available in different weights such as 30, 40, 60, even 80+ weights. The lower the number of the weight of oil the thinner the fluid.
These shocks and the entire suspension setup are not just for show. They play an integral role in how the RC handles and how well it performs under different terrain conditions. The suspension setup on these types of RCs as a whole also has a lot of variable options. This allows the owner a lot of leeway when it comes to tuning and tweaking. You can adjust things like ride height and rebound rate of the dampener shocks due to the type of oil used and the strength of the coil spring (which in some cases is indicated by color).