I'm finding the default medium insert too small. I'm currently using the large insert.

My Shield doesn't have inserts but I do have other brands that do.
Use whichever one allows your trigger finger to rest on the 'Sweet Spot' of the trigger which accomplishes a straight rearward trigger press.

Since everyone has different size Hands/Fingers, the insert that works for one, may not work for another.

The next to smallest one that measures 1.175" wide. I have large hands, and can't imagine anyone but someone that wears size Large-and-a-Half glove size being happy with the large insert.

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Dave Brown
SWCA #3279

Tried Large and Medium/Large and went back to Medium. So, for now anyway, Medium seems to be working best for me.

It's funny, but large works best for me. And I don't really have large hands. With the medium grip, the second pad of my finger is on the trigger. Not the first pad as its supposed to be.
BTW, I am talking about my M&P Compact 2.0.

Hickok45 hands here and I use the Large 2.0 backstrap on my gen 1 with granular Talons trimmed to avoid the backstrap. I like the width of the large.

I have big hands, and the Largest always feels the best in my hand ----- butttttt, I shoot it better with the med or med large. Go figure!