Drivers plug a device the size of a garage door opener into the on-board diagnostic (OBD) port of their car. The device records and sends the driving data to Progressive, and Progressive uses that information to calculate the rate. After 30 days, customers find out if they're eligible for a discount based on that 30-day "snapshot" of their driving habits. At the end of a six-month policy period, Progressive calculates the customer's renewal discount and customers return the device to Progressive. The company doesn't take into account how fast the car goes although it does take into account how fast and frequently the vehicle operator brakes. Snapshot is voluntary and customers can opt out at any time. The customer is charged up to $50.00 if they do not return the snapshot device to Progressive should they decide not to engage in the program after receiving it.