The ceramic beads built into the necklace disrupt the tick's receptors, making it impossible for it to detect the dog. They limit parasitic infestation and make it possible to reduce the applications of anti-parasitic products. The necklace is available in three sizes: XS - Mini: for a neck size of 15-25 cm S - M: for a neck size of 22-38 cm L - XL: for a neck size of 38-60 cm Attention: there is currently no treatment that is 100% effective, even chemical! In the event of a heavy infestation in your region, you can combine several natural methods for optimal protection. Stay alert! Additional information: once out of the pouch, thread it around your animal's neck and, using the clasp, adjust its length by making sure to respect a space of about 2 cm between the neck and the necklace. Duration of effectiveness: The cord: about 2 years. Pearls: about 10 years. Eco-Friendly Zero waste objective Cruelty Free