The Good Pup is an official Fi maker for Fi-compatible dog collars! We use genuine Fi collar end links that will fit your series 3 Fi tracker. No longer worry about your pup taking impromptu, unsupervised adventures! Fi features escape detection, real-time GPS tracking no matter how far your dog roams, and built-in AI tech features. Fi's tech combined with our stylish flair will provide your pup with the most stylish and safe collar on the market.