This insert design allows each user to adjust and fine-tune his insert block to perfectly fit his particular pistol. Not only does this allow us to support almost all gun types with just two models of inserts (Type-A and Type-B), but it enable users to adjust for the small variances that are often introduced by the gun manufacturers, who don’t consider the external dimensions of the trigger guard to be critical. This has always been an issue for the Alpha-X inserts, and this problem is now solved with the new Flex insert design.