This Standard specifies requirements for towballs for towing vehicles of up to 5 t towing vehicle mass. The towballs are intended for towing trailers and caravans of up to 3.5 t aggregate trailer mass, for use on public roads.The method of determining the static strength of a shank-type towball is given in Appendix A and the dynamic strength of a towball is given in Appendix B.NOTES:1 Towbars and coupling bodies are specified in AS 4177.1 and AS 4177.3 respectively. 2 Requirements for off-road applications are beyond the scope of this Standard. 3 Requirements for shank-type 50 mm towballs only are specified. 4 Towing bracket and towballs complying with ISO 1103 and ISO 3853 are also acceptable.