Mugen super silicone shock oil is used to fill shocks and add resistance. Clear shock oil. Mugen shock oils are super consistent and are rated in cps. The cps system is used in Europe more than the US and is different than the Associated oil's system of WT. Even the cps system from manufacturer to manufacturer can different for real viscosity or thickness. Its best to choose a single manufacturer's oil so you can create repeatable setups with your car.