I believe it is. After I took the taillight assembly out (which is easy), I reached down thru the opening to see if the bottom of the inner wheel well was wet. I didn't find any moisture, which was a big relief. The old gasket was so badly worn & dried out, it probably wasn't providing any protection at all. Don't know how long the gasket was degraded. I hardly ever drive the car in the rain & I keep it covered with a weather-protection car cover in the driveway. So the PS taillight probably hadn't seen any large amounts of moisture for awhile. Lucky me!