PC players, get Double Station Cash between March 29th-31st when you buy Station Cash or redeem an SOE Pre-Paid Station Cash card.* Stock up on Pre-Paid Station Cash cards now to take advantage of this special offer!
*Offer valid from 12:01 AM PDT March 29, 2013 to 11:59PM PDT March 31, 2013. Double Station Cash offer excludes purchases made via SMS.
Source: DCUO Official forums