For want seems like 20 years now, I keep seeing mountain bikes and 10 speeds on roof racks and the back of just about every kind of vehicle imaginable. And what I also see, is plastic grocery bags covering the seats. I want to know why. Is thee a major theft ring for bike seats? Does it make them softer? Harder? I question this because I have my mountain bike in the bed of my truck and the seat is above the roofline. I know it's not blow off prevention, because it's sustained some serious speed tests back there. What gives?