magnesium
One problem you can have is if the bit is dull it can cause a firre if it gets the magnesium too hot (rare i f you use a lube ) but if you drill it then the hard anodizing is gone and it can shine more.
If you want a bigger peep order one and sell the one you have.
Heck I am thinking of getting a meta peep,, just gotta figure out what size I have on my bow.
you should see the outer ring of your sight in the peep, one thing I have found with many people is that they use a kisser and it doesnt allow them to see the ring. My dealer got me into anchoring to tip of my nose and whe ni did that on my Parker I was getting the kisser driven painfuly into corner of my mouth. No kisser=happy, now.
Good Luck and Good Shooting.