I always bring 4 balls, with either a RotoGrip Grenade or Storm Super Natural for my weakest ball. Most nights I will end up using 3 balls, because my heavy oil ball doesn't get enough oil, but I bring it anyway, just in case. Also, for me, it's easier to load and unload 2, 2 ball bags (stacking 4 ball Storm Rolling thunder) than one 3 ball roller, weight-wise anyway, plus there is pockets and space galore for anything else I bring.