Using these for years, works great - UTG Pro Model 4/AR15 Receiver Wedge

I have been using these in my rifles for 10+ years. They take the upper/lower slop out and snug up the receivers nicely. The first time it is installed it is a little tight, but it softens up shortly thereafter. My most recent purchase was for my son who noticed the difference between mine (with) and his (without). He now has this installed as well.