I Replaced some OEM plugs on Tundra 5.7L with 90K miles. Vehicle was running good, just routine maintenance. Plugs shown as removed from engine with the front of the engine being at the bottom of the page. I was shocked to see cylinder #4. Half the insulator was gone. There was not miss or hesitation in the engine with these plugs. Even did a cylinder deactivation test with these plugs and the engine run rough when any cylinder was deactivated. From the condition of that plug it look like it may have been like this right from the factory. Surprised vehicle ran fine and smooth like this. Just thought I would share.