Frankly, I’ve got no idea lol. I just stuck a sturdy looking sewing needle onto a drill and went to town on that vent. Just drilling into it until I thought it was enough. I think it’s a really tough mod to do without some specialized equipment (micro drill). I ended up liking how they turned out, but there’s definitely a high chance I could’ve made them sound like ass or just drilled through the driver. The bass definitely got reduced plenty though 👍.