This style of coupling, usually suited to a 50mm Australian Standard tow ball, is suitable to be used where either there are no brakes fitted to the trailer or the braking system does not require activation from a sliding or overrun coupling. AL-KO couplings are simple to attach to the towball and provide safe secure attachment of the trailer to the tow vehicle. Typical applications for domestic trailers are up to 750 kg loaded mass, where no brakes are required. For independent brake systems such as electric or power operated like the Sens-a-Brake system for marine trailers over 2000 kg, a fixed coupling is the appropriate selection. Fixed couplings for 50mm towballs are suitable for up to 3500 kg total laden trailer mass as long as the appropriate braking system is fitted to the trailer.