Unbraked couplings for 50mm ball brackets are manufactured either in pressed steel or cast iron. The cast iron option is more rugged and better suited for constant use applications.
Many trailer users prefer the security of the 'double locking' principle, so that in the unlikely event of the coupling failing in its primary function, the safety catch should prevent the coupling from becoming detached. The pressed steel product is however, perfectly sound and is used extensively on economy and leisure trailers.
The unbraked coupling is usually (though not exclusively) connected to a straight drawbar system and can be fixed by either bolting to or welding on.