Generally speaking, we recommend installing five pair per linear mile. Stored fiber length is dependent on how far apart a pair is installed, with the total slack stored equaling twice that distance. In a typical span, a pair will store approximately 150 feet of reserve fiber. Opti-Loop® FOS snow shoes are only sold in pairs. Beyond slack storage, Opti-Loop® FOS snow shoes should be installed at splice locations to dress cables on the strand.