From the article...
"you simply remove the plate and mount the optic of your choice with the appropriate mounting plate."
Not necessarily true. The Firefly does not come attached to the slide.
It is "packaged" together. You are given a tiny wrench and instructed to remove a plate from the slide, install the Firefly plate etc. OK if you can get the plate off. I ordered the gun 26 April, received it 16 June and sent it back to Springfield 18 June to have them remove the plate and install the Firefly. 1st time and last time I purchase a firearm based on trust. This is my 4th Xdm. Never thought I'd be installing a sight. My fault. I've emailed Springfield but, as usual with their email, have not / do not expect a response. Called the customer care number and got a quick response. Great people there. Send in the slide. No one local in my little town (Chicago Il) to handle the work. Wait another 4-6 weeks. Thank the Lord I do not need this gun. Knowing what I know I would not have ordered the gun, and likely would have went with another choice, not necessarily Springfield.