This CZ extender adds extra length and flexibility to your favorite tennis necklaces, ensuring the perfect fit with extra sparkle.Works specifically with our 2.5mm and 3mm tennis necklaces with the same clasp. Is not universal. Pairs perfectly with the PERFECT TENNIS 2.5MM CZ NECKLACE, PERFECT TENNIS 3MM CZ NECKLACE, and the HOLLYWOOD STATEMENT NECKLACE.