It depends on which of the progressives you’re playing. Holmes And The Stolen Stones and Jackpot Raiders both feature 5 jackpots which can be won by collecting 5 gems of the same colour. Empire Fortune uses a jackpot wheel and awards the biggest (Empire) jackpot for landing the joker symbol on the top one. In Joker Millions, you’ll have to fill the screen with 15 jokers in order to collect the main prize; the probability of winning the jackpot is proportional to your bet size.