maple leaf vsr arm review

I have a Bar10, So Im just wondering what is the use of Maple Leaf's I-key that comes with the Maple leaf hoparm. What is its function?? Do I still need a hop tensioner or the hop nub?? Whats the difference between the hop nub and I-key? im really confused. thankyou!

So i guess i won the Maple Leaf Lottery:D Received my concave arm, didn't seem to have misaligned nub or something else, luckily. Arm was a tight fit at the pin where you attach the arm, although it didn't need hammering. However, the other end still wobbled a bit so i wrapped some ptfe tape...