I bought these washers because when I wanted to upgrade the front end of my King Arms M4A1 the aftermarket barrel that I attached had a bit of movement. It is a good idea to purchase this product because outer barrel wobble can bend your inner barrel and also disrupt the connection between your hop-up unit and the air nozzle. Plus using these washers is much cleaner and more reliable than tape or even rubber O-rings. I have only tried this product with my M4 platform so I am not 100% positive it would work with similar M4 variants. This is a very inexpensive purchase that will add to the completion of your custom guns.
Six washers included
Fixes any barrel movement that you may have with your gun
Multiple thicknesses are included to fit your needs
I have not experienced any negatives with this product.
Rating: [5 of 5 Stars!]