The 22mm to 17mm ball adapter is perfect for turning your old reliable Garmin mount into one that is compatible with a new larger GPS. Simply screw it onto the existing mount and it will fit the 22mm socket on the back of the cradle that came with your GPS. Note: These only fit GPS devices that utilize the 22mm ball size. Only the items listed in the title will fit this adapter. The majority of Garmin GPS devices use the smaller 17mm ball size.