activity diagram - showing multiple objects passed between two actions

activity diagram - showing multiple objects passed between two actions

I have one action (action_a) that calls an operation(operation_x) on
another action (action_b).
The parameters to operation_x are as follows:
action_b.operation_x( param_1, param_2 )
Question: How can I show multiple objects being passed? Does the following
approach make sense, or is there a more standard way?