Does CT sensor match with main cable?

Can anybody say something about my main cable if it fits the CT sensor? To me cable is too thin. Does it matter if the cable does not fit tight?

In fact, ferrite-core c.t’s must NOT be a tight fit on the cable, because ferrite is a brittle material and any stress will snap the core, rendering the c.t. useless.


Is that main breaker really marked as 40A? If so, those cables are seriously undersized.