Akwai rassan gami da aluminium sarari guda biyu a tsakiyar bayan samfurin wanda ya dace da lanƙwan jikin ɗan adam.Tsarin ergonomic, baya ya dace da jikin mutum, kuma yana da dadi don sawa, wanda zai iya taka muhimmiyar rawa wajen gyaran gyaran gyaran fuska.