The OEM part has snap-in tangs on the three prongs (they broke on my car's stock part, which is what prompted this Thing). My part doesn't have the tangs, (they'd probably break) but it's a tight press-fit. You could also glue it with hot-melt, blu-tack, or something more or less semi-permanent if you like.
The prongs are very fragile and tend to break during support removal if you're not careful, but they're not really necessary anyway.
The stock part has an o-ring, and this Thing includes a recess for it.
Good application for acetone-vapor smoothing, which was done on the parts shown.
Also a good application for pause-and-change-color, which was done on the part I settled for in my car.