Probability education has fast become a contested area, with curriculum authorities in some countries recently suspending its introduction until the post-primary years. In other countries, children as young as 7 years are introduced to informal probability concepts. These recent international shifts in practice have contributed to a paucity of attention to the understandings of probability among pre-service and practising teachers. This presents implications for teacher educators who seek to provide opportunities for pre-service teachers (PSTs) to develop appropriate knowledge for teaching. This paper reports on the probabilistic understandings of a sample of 104 elementary PSTs. It focuses on one particular aspect of this knowledge -- understanding of probabilistic fairness. The study examines the approaches taken by PSTs when designing fair and unfair activities for use in the primary classroom. We place particular attention on the variety of random generators selected and the features of the activities designed by PSTs to illustrate fairness. Almost half of participants successfully designed fair and unfair activities for three different random generators. Particular random generators, namely playing cards, dice and coins presented more challenge and less successful outcomes. The findings provide an initial step in unravelling the complexities of understanding probabilistic fairness and serve to inform the design of curriculum experiences in probability instruction in initial teacher education (ITE) contexts.