DRIFT SOCK

Does anyone use a drift sock, when fishing in their v20?

If so:

1) What are you fishin for?

2) When do you use it (under what conditions - wind, wind with current, wind against current)?

3) What make and model do you have?

4) Where did you get it? (Cabelas would be a plus for me)

5) How much did/does it cost?

Thanks.