There is a shiny metal "jaw" on one end that keeps the rubber insert in place. You can do this with just your hands to crimp the jaw and allow the entire insert to slide off.
Note that not all inserts are created equal, so be very certain that you are purchasing the correct size.
It is easier to just buy the whole wiper assembly, but I like the OEM units...if you look closely, the vehicle model is embossed on the top!
