Really neat foregrip, vertical only w/ 3x finger grooves. It has a dedicated top groove for the index finger whilst the lowest-most of the foregrip has a forward slant to serve as a rest for your small finger. The backstrap of this grip very gradually broadens out toward the bottom, featuring a double row of grooves down the height, separated by a spine.

The side panel insets are faintly textured and slot in via a dovetail. These panels can only be removed by threading the bottom end cap off. The bottom cap has an O-ring around the bottom-end to prevent ingress. By removing these, you can affix the pressure pad strip from a flashlight remote coil. Please note that the aforementioned insets can only be inserted in one way. If you feel these panels offers abnormal resistance, turn them around and try again. They should go in smoothly. You'll also see that the UTG logo on the panel has to be upright, which can be used as an upright guide.

Furthermore, the aforementioned threaded insert tube has an interior battery compartment that can be removed by means of a flat drive, corresponding to the slot right at the bottom. Once removed, a cylindrical compartment is exposed, wherein one could carry spare batteries. There is likewise, a compression spring on the flip side of this cap, to keep the stored batteries in a compressed state, so that they do not shake around and likewise, absorbs vertical vibrational force.

The battery compartment here can house 3x (R)CR123 batteries, although you'll need a little force to get the cap into the threading position. With three of the aforementioned batteries inserted, you won't need to worry about them shaking around at any time. With only two of the aforementioned batteries, you'll definitely experience some shaking of the batteries inside.

* Please note, 18650 batteries fit very hard inside and we don't recommend trying to slot these in, as you might not be able to get them out again.

The Picatinny mounting section has an opening for a crossbolt to retain the foregrip onto male Picatinny rail that way, although neither of the two holes are hexagonal, so if you make a plan w/ a machine screw and a nut, the latter is not going to sit flush. Both holes are slightly over 6.5mm is diameter.

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Info from the internet relating to this product;

Tactical Ergonomic Foregrip with Pressure Switch Area & Battery Compartment.
The Front Grip is 5.4 inches in height from the base, the side profile is 1.8 inches wide near the base, 1.4 inches at the thickest dimension,
Weighs 6 ounces.
This is an excellent choice for those mounting tactical lasers or lights.

• Fits hand guards equipped with a Weaver or Picatinny rail system. Non-slip Features
• Battery Compartment (AA Batteries 2 each or 123A 3 each)
• Pressure Switch Housing both Right & Left sides
• Moulded from reinforced plastic composite.
• Great for M4, AR15, M16, AK47, MP5, GSG5 with tactical rail

Picatinny Mounting Deck to Slide on and Screw Tight
• Ergonomic Finger Grooves for Most Comfortable Grip
• Tactical Pattern Accenting a Cool Look
• Clever End Cap Conceals Battery Storage and Controls Grip Mounting
• Practical Side Slides Allow for Ambi Use of Pressure Pad

Technical Specifications;

Short product walk-around and review can be perused here;