The recoil spring has been redesigned and is suppose to last longer, the backstrap has interchangable inserts to custom fit your had...a couple other things as well. All in all it's a Glock, shoot the crap out of it and enjoy her!!
The smallest back strap is integrated in the GLOCK MBS Frame reducing the trigger distance of the standard size frame by 2 mm. The medium back strap is a 2 mm back strap offering equal size of a standard frame. The large back strap is a 4 mm back strap.
The magazine release catch of the Gen4 is reversible and enlarged. The reversible magazine allows users to switch the catch to the left or right side of the pistol with no additional parts.
Additionally, the Gen4 has a new Rough Textured Frame (Gen4 RTF) surface designed to enhance grip traction and is present on the frame as well as the interchangeable back straps.
Internally, the original recoil spring has been replaced with a dual recoil spring assembly. The dual recoil spring assembly noticeably reduces the recoil while simultaneously increasing the life cycle of the assembly. .