The smallest back strap is integrated in the GLOCK MBS frame reducing the trigger distance of the standard size frame by approximately .08 in. The medium back strap adds approximately .08 in. - equaling the size of a standard frame - and the large back strap increases trigger distance by a total of approximately .16 in. The magazine release catch of the Gen4 is reversible and enlarged. The reversible magazine catch allows users to switch the catch to the left or right side of the pistol with no additional parts. Internally, the original recoil spring has been replaced with a dual recoil spring assembly. The dual recoil spring assembly noticeably reduces the felt recoil while simultaneously increasing the life span of the assembly. Additionally, the Gen4 has a new Rough Textured Frame (RTF) surface designed to enhance grip traction and is present on the frame as well as the interchangeable back straps.