Like the anatomy of a male whale.
It's phallic no matter how you slice it.. Ouch. It fits into the far reaches of your boat where no regular man can reach.
You put your gear in it and roll up the top. Then the air purging begins. There you are frantically fighting it like you did when you got a boner back in High school math class and the teacher asked you to approach the board to solve an equation. Then you get to shove that long wedge shaped cylinder into the open cavity of your boat. Get where I am going with this?
They are one of the most useful bags you can get for kayak touring. If you don't own one of these bags you just don't know what you have been missing.