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A slap ring is a half-open metal sleeve with a special crank that is placed over the thumb. The slap ring is a stop aid for bass players . The effect unfolds through the weight and in combination with the centrifugal force . Gerhardt Claassen-Reese has had a German patent for the slap ring since 1997 (DAKZ 19639088), which has now expired due to non-payment of the annual fee.
