Bow Jax Speed String Sleeve Black 4pk.. Can be used with or without string silencers. Eliminates the need for speed buttons. Silences while improving speed. Installs by slipping over the string(bow press required). Weigh 16 grains each. 4 per pack. Package Contents: Bow Jax Speed String Sleeve Strategically places weight on your bowstring to gain velocity. Can be used with or without string silencers. Eliminates the need for speed buttons. Silences while improving speed. Installs by slipping over the string(bow press required). Weigh 16 grains each. 4 per pack.