I purchased the Chevrolet GM OEM Ignition/Doors Lock Key Cylinder Set with Keys and it fits and works perfectly on my 2004 Chevy Silverado. The ignition cylinder is quick and easy to install. The matching door lock cylinder replacement is a bit more challenging. I highly recommend you have / purchase an auto panel-trim removal kit from Amazon (as I had) to properly remove the interior door panel without damaging it. I also used a remote camera / endoscope I bought from Amazon to see within the tight space between the interior / exterior structural door sheet metal so I could remove the small metal wire clip that secures the door lock cylinder in place (and remove the adjoining plastic clip that moves the lock linkage as you rotate the lock with a key). Recommend searching for some of the online videos on the cylinder switch, and door look installs (if you aren't experienced with this) before you tackle but changeout is easy for older vehicles that do not have coded / computer chipped keys that have to be programmed. As for "security", I gave a 4 star rating simply because there really is no "security" programming / wiring required to install this switch and key on a vehicle that does not have embedded security chips.