We recommend that strings and cables be replaced at your local pro shop or the Ravin Service Department every 2 years or 400 shots. If you elect to replace the strings and cables use only the Ravin Press. Do not use the Ravin Bow Press on any other crossbow. Carefully read the instructions and its warnings supplied with the Ravin Bow Press before use. For use in R500 R500E R500 Sniper and R500E Sniper only.