Specifc coupling designed to reduce trailer sway. This 50mm ball type fixed coupling is designed to be used on trailer up to 2500 kg ATM (total loaded mass) and with a maximum tow ball weight of 250 kg. This unique product incorporates a clamping system that grips the sides of a specially designed 50mm towball and resists movement of the trailer. This action slows down any tendency for the trailer to sway or veer from a straight condition. This is particularly beneficial when large trailers such as caravans are buffeted by side winds or by a passing truck and trailer combination.