Refer-A-Friend Card

 is a limited-time premium consumable released for the Burns' Casino 2016 Event. It increases the amount of event currency received from tapping Casino Gamblers in friends' towns. Once purchased, its benefits last until the end of the event.

Its cost varies depending on the Act the is purchased, from 90 Donuts in Act 1, to 60 donuts in Act 2 and lastly for 30 donuts on Act 3.

Trivia

 * It's the second type of friends' rewards booster to reduce its price depending on the act it's purchased.
 * The first one being the Dumping Permit during the Monorail 2015 Event.
 * Doubling rewards from neighbors' towns actions, the player could get a maximum of 1780 Red Chips, Green Chips, or Blue Chips (instead of the usual 890) per day.
 * For 13 days, the duration of Act 1, it meant an additional of 11570 Red Chips.
 * For 10 days, the duration of Act 2, it meant an additional of 8900 Green Chips.
 * For 12 days, the duration of Act 2, it meant an additional of 10680 Blue Chips.
 * This adds up to a total of 31150 additional event currency that could be obtained with the card through the whole event.