Rigid Coupling Elements Rigid Couplings with Taper Bore bushes provide users with a quick and easy fixing of rigidly connecting shafts with the convience of a wide selection of shaft sizes of the Taper Bore bushes. The male flange can have the bush installed from the Hub side (H) or from Flange side (F). The female always has the bush fitting F which gives two possible coupling assembly types HF and FF. When using on horizontal shafts, select the most convenient assembly. When used on vertical shafts only use the FF type. HF style (Hub & Female Flange) FF style (Hub & Female Flange)