Beaver Puff ‘string silencers’ made from water-repellent beaver fur are high-performance absorbers for your string and are used by many archers worldwide, especially in the US.
Upon loosing the bow string, a bows limbs return to their original shape and the energy released is transferred to the arrow propelling it forward. However not all of the kinetic energy is transferred to the arrow. Some of it passes through the bow and the string, which is what you can hear -the twang- and see in the string vibrating. A ‘silencer’ helps disperse some of the energy that is left in the bow and absorb the noise.
Sold as a pair with assembly instructions.