Back Extension: Kukula kwa chubu 50x100mm, ndi makulidwe a 3mm, olimba kwambiri komanso osasunthika, kapangidwe ka akatswiri ochita masewera olimbitsa thupi.Pakupanga, amapangidwa ndi utoto wa Standard 3-layer.Standard 3mm makulidwe chubu.makina olimba kwambiri okhazikika komanso olimba.Zidzatengera inu mwatsopano maphunziro kumverera pa masewera olimbitsa thupi.