How many live crickets can i feed my rats?

so 4 out of my 5 rats have just tried live crickets for the first time. they went crazy over them. how many can i give them say once a week as a treat. dylan and tamaki had 3 each (not sure what size crickets they are. probably 1 to 2", maybe smaller) and gizmo and beezley had 2 each. bailey had none since he was still in bed. lol