We recommend replacing strings and cables at your local pro shop or through the Ravin Service Department every 2 years or after 200 shots. If you choose to replace them yourself, only use the Ravin Press. Do not use the Ravin Bow Press on any other crossbow. Be sure to carefully read the instructions and warnings provided with the Ravin Bow Press. It is intended for use exclusively with the R500, R500E, R500 Sniper, and R500E Sniper models.