T-money card

With just one T-money card, there is no need to carry a wallet.

You can quickly pay and go at various places without waiting in line for your change, receipt, or signature. T-money is safe, quick, comfortable, flexible and reliable.

You can pay 900won even 2times to take a bus or train before 30min.
Don't need to pay when you take a bus again.

We will lent T-money card for free at seoul backpacers.

source
http://www.t-money.co.kr/