[thom4782]

The holes at the top are about the size of a dime or a nickel. I don't know how much they narrow as they go down to the underside of the car.

The drains can get clogged when leaves dry out and break into pieces that fall down into the tubes. Eventually these pieces will stick together clog up the drain much like hair might clog the drain in a bathtub.

My drains were pretty clean. Even then I tested them by pouring water into the holes and watched how rapidly the water drained out the bottom. The water flowed quickly. After I saw all was well, I followed this up by installing two drain screens in that I ordered from Suncoast in the rear drains.