You can switch 2 SIM cards without turning off the phone and no need to cut your SIM card with the convenient and useful dual SIM adapter. An interface ribbon cable connects the micro-SIM card tray (SIM 1) to a standard SIM card adapter (SIM 2). It folds around the back of the phone to a place where the case holds them in to position. It is very useful for Iphone 4 / 4S. - Easily to switch 2 SIM cards without turning off the phone - No need to cut your SIM card - No data loss when switching 2 numbers or turning on/off the phone - User friendly option menu will embed into your phone menu system - The extra SIM card slot is standard SIM card slot size - Very simple operation easy plug & play - Compatible with Iphone4 / 4S