Abstract: The invention relates to a safety spacer for a bicycle, having an arm one end of which has a reflector and the opposite end of which is fastened to a two-part split member by means of a shaft. The parts of the split member, when assembled, form a shouldered circular circumference. The safety spacer also comprises two fastening lugs which, when pressed together, form therebetween on the one hand a cavity with a shouldered circular circumference for receiving the parts of the split member and for attaching the same and on the other hand a circular aperture for attaching the safety spacer to a tube in a bicycle. The arm can be swiveled and pivoted freely, and all the parts of the safety spacer can be linked together and attached to a bicycle by means of one single screw.