Tokyo Marui just announced that they will finally release the new M4A1 MWS ZET at the 13th of November 2015. The gun was already announced for 2014, but they recognized some problems with the durability.
THE TOKYO MARUI ZET SYSTEM
The new improved design has a innovative shock absorbing mechanism for the bolt catch.Its called the ZET SYSTEM! ZET = (Z) ULTIMATE ENDURANCE TECHNOGY. Check out the video below for a better understanding of the new system.
TOKYO MARUI ZET SYSTEM – PRODUCT VIDEO