Source: https://www.amazon.com/Spuddys-Premium-Flea-Prevention-Collar/dp/B074W28B3H/ref=pd_day0_199_6?_encoding=UTF8&pd_rd_i=B074W28B3H&pd_rd_r=4DKMG7Q913MKC45M743R&pd_rd_w=Yvvcm&pd_rd_wg=eGY81&psc=1&refRID=4DKMG7Q913MKC45M743R