The Timber Creek Outdoors Enforcer AR Pistol Grip does not have any inserts for the cutouts on the grip. Some people with skeletonized grips will interlace paracord in the grip. Here are some other options for grips that have more gripping texture and surface area.
https://www.opticsplanet.com/hogue-ar-15-m-16-rubber-grip-with-finger-grooves-od-green-15001.html
https://www.opticsplanet.com/hogue-ar15-m16-g-10-od-green-camo-15168.html
https://www.opticsplanet.com/fab-defense-ergonomic-pistol-grip-for-ar15-m16-m4-hand-guards.html