Hitch adapter in case the regular hitch does not fit. 6 in. L x 4 in. W x 5 in. H (3 lbs). Please note that on all Quick release type axle and bolted axles the regular hitch fits very well. In case you have an internal hub gear (a very small of bikes in North America have them - like some Electra bikes) the regular hitch does not fit and you need this hitch adapter. This hitch adapter connects to the rear stay instead of the axle. If you prefer this type of connection this might be a solution for you. The hitch adapter consist of a bike and a tow bar attachment. The bike attachment connects permanently to the rear stay and the tow bar attachment replaces the regular part of the tow bar. This is the solution for some electric bikes, while on a large number of electrical bikes the standard hitch does fit.