Open Box ES Field Flattener For f/5 to f/7 RefractorsCondition: This is an open box return in excellent condition. The outer body is unmarked and the optics are clean. Though, this is missing and does not include the M48 adapter. Otherwise it is practically new and includes the original box. Description: This is a field flattener for refractor type telescopes with a focal ratio of f 5 to f 7 Causes no change to the telescope focal length 2 inch barrel to easily attach to a two inch focuser Fully multi