For anyone looking for a good iPhone Tripod mount, be sure to consider the RetiCAM smartphone mount. It's more expensive then some of the other ones out there, however it's built extremely well.
https://www.amazon.com/gp/product/B00P4VAHAI/ref=ox_sc_sfl_title_1?ie=UTF8&psc=1&smid=A131AJJ2D0Z6UZ
https://www.amazon.com/gp/product/B00P4VAHAI/ref=ox_sc_sfl_title_1?ie=UTF8&psc=1&smid=A131AJJ2D0Z6UZ