The 
NUPROL Ergo Foregrip (RIS) in Black
 is an angled, low-profile airsoft grip designed to improve rifle stability with a Picatinny rail interface. It is made from a high-strength polymer and features a storage compartment in the base. 
 
 
Key Features and Compatibility
Design and Use: The angled, low-profile design is intended to provide an excellent handstop, facilitating the popular "C-Clamp Grip" technique.
Material: The grip is made from a durable polymer material.
Compatibility: It is compatible with all standard 20mm RIS (Rail Interface System) or Picatinny rails.
Installation: The grip slides onto the rail and a screw at the base is used to tighten and secure it in place. Some users have noted it can be a very tight fit requiring some force during installation.
Storage: It includes a small storage compartment at the base, useful for carrying small items like extra batteries into the field.