You'll need an ergo grip - Troy Enhanced Trigger Guard

The Troy enhanced trigger guard is well made, offers a ton of room and is very wide. But it has a problem. It creates a large gap right where your middle finger knuckle will rest. If you're familiar with "glock knuckle" it will create a slightly worse effect. You can buy a houge or ergo grip that has a bit that will fill this gap and ergo makes a thing called a gapper that will fill the gap if you already have a grip that doesn't have a gapper...like a standard magpul grip will cause this guard to bit your knuckle.

It's built really well, but there are options that don't require additional steps.