Look, with the exception of the TS hood, the vents are all surrounded by raised ridges so 90% of the water is channeled around the vents with the exception of the smallest vent closest to the windshield.

As long as you are not shooting water directly into the vents, very minimal amount of water will get inside. Even so, it doesn't hurt anything.

 

The real Mugen Hood can handle water. It has a rain gutter.

 

I did go to their site. But from the two pictures they've posted, I couldn't see the bulge due to lighting of the picture. Thanks for answering my question.

 

the seibon mg hood comes with a rain blocker/guard that you could attach as you need.

i don't use that, and it's fine.

only thing i would suggest is getting a cover for your battery. one of the hole on the right side of the hood is right over the battery.

Also, i wouldn't recommend any sort of open intake filter without the stock cover. I have my stock airbox. I checked and the water does go right on top of it when it rains. I would imagine that it'll soak your intake and you'll have hydrolock with a bad luck.