San Francisco gets a lot of rain and city dust. I have two exercise bikes on my balcony, one of which is big enough for six outdoor plastic recliners. Last week, my family stayed in the room, so I had to put the exercise bikes on the balcony. The second cover covers the exercise bikes and holds them in place. There are two ties running diagonally across the bottom of the cover. My balcony is on the 14th floor of a high-rise apartment, so the cover doesn't fly off when I tie it to the bike, which is fantastic 8-)