About the Rail Mounted Vertical Foregrip Rail mounted vertical fore grips are one of the most popular airsoft accessories for most airsoft guns. Vertical foregrips really came about and became prevalent after the mid 90s when they were being developed by Naval Surface Warfare Center Crane Division. The grips were developed for the Special Operations Peculiar MODification (SOPMOD) M4A1 carbine. The grips provide extra control and better ergonomics for the M4 carbine. They fit on any airsoft gun with standard spec picatinny style rails, so they aren’t just for use on M4 or M16 variants. They are made out of durable polymer and have a tightening mechanism on the bottom along with a witness hole on the side to make sure you are aligned in the rail slots. While there is a slot on the bottom of the grip for tightening the grip, I would recommend only tightening with your fingers using the knurled portion of the grip. Over tightening can strip the internal threads. We get these in from both Lancer Tactical and NCstar. What's Included In The Box:  Rail mounted vertical grip Quick Overview: Rail mounted vertical grip Fits standard picatinny style rails Polymer construction                                                 Warranty:  FOX AIRSOFT OFFERS A 30 DAY WARRANTY AND REFUND POLICY WHICH YOU CAN READ MORE ABOUT HERE.