Twitter has unveiled an online currency of sorts, the “twollar,” aimed at boosting charitable giving, the Guardian reports. Twitter users start out with 50 twollars (the equivalent of $5), which they can award to other users for astute posts and the like. Twollars are currency, but only charities can sell or redeem them. So if you run out of twollars, the only way to get more is by giving. The idea has already raised $1,500 for Charity Water.