Low profile Suntunnel

Here's the TSR unit (Velux Suntunnel).

The upper tube is identical to that of the TMR previously mentioned. It also goes in from the outside.
But where the TMR has a separate inner collar, this one presses directly into place, so there's no additional angular adjustment. A thin weather-stripping goes on the lip for a snug fit. If the sun orientation is good, or when installed at a shallow roof pitch (I'd say 5:12 or less), the smaller appearance is actually nicer.
The only caveat is that the flashing, which is integral with the black collar just like in the TMR, is entirely symmetrical, making topside-down installation possible. It would put the collar weep holes on top instead of bottom. Sure there's a label, but sometimes roofers ignore labels.
This one is for the new Powder Room. It's the only one that's plainly visible from the front, so I figure a low profile is best.

Purchased off the shelf at Home Depot ($162 plus tax). Click on image to track back.