This listing is for a set of 10. These barbwire arm extensions are three-strand and are installed onto existing fence - PVC (vinyl) or wood - and any other existing structures to include post, fence, brick, concrete, wall, etc. These vertical flat mount barbwire arm extensions measure approximately 14" long. Fasteners are not included as fasteners vary depending on which structure you are installing the extensions onto. For any questions regarding installation or fastener recommendations, please contact our customer service department. You can reach us directly via e-mail at extendapost@gmail.com