A fastener for anchoring in a hole, for example a tube end whereby a component may be secured to the tube, has an outer expandable collar (10) having a tapered inner surface (11). An inner expansion member (20) is provided that has a complementarily-tapered outer portion (23), and that is arranged to be drawn into the collar (10) for securing the fastener in the hole. The outer surface of the collar (10) is smooth, and is advantageously for use with an accurate, smooth hole, whereby the securement is effected purely by friction, thereby minimising undesirable stress concentrations. The tapering of the collar (10) and expansion member has an included angle of 16° to 30° further to enhance the frictional retention.