When choosing the protection of crankcase, it is necessary to pay attention not only to the material from which it is made, but also to a number of technical features.
First, the protection must have an opening for discharge of oil. This will make it possible not to remove it every time you change the oil. Second, the protection shall be secured directly to the body, not to the tugs.
As for the material, there are two options on the market: glass-plastics and steel. Composite protection is lighter and does not rust, but is prone to cracks. The steel shall be protected against the impact, but may not be cracked. The cols are better off so that rust doesn't spread.