Seismic isolation is an effective method in reducing the seismic response of structures, and its main purpose is to provide the conditions for continuous use of the structure after a severe earthquake.However, due to the high costs of this technology, its use in ordinary buildings has not been significantly expanded.One of the relatively new types of separators are elastomeric cushions armed with fibers (fiber isolators) which, due to their technical characteristics, will have the necessary economic justification for use in ordinary buildings.This article, while introducing fiber separators that are used independently and mentioning their advantages for economic use in many ordinary buildings, examines the analytical relations provided by different researchers to calculate the lateral stiffness of these separators and compare the results of these relations with laboratory studies ,will pay.And finally, she tries to choose the most optimal analytical relationship to calculate the lateral stiffness of unbonded fiber reinforced isolators.