I've got the Dominator with the I/O harness, Input Harness, and Output harness. I'll have enough I/O's, but with all the wiring I've got ahead of me, the thought of cutting a few extra connections off the task list seems like a good thing. Of course, when all is said and done, I am sure it would be worth the extra effort.The 3 relay bump takes two inputs and 3 outputs. Here was my first time testing it.