Just another friction-fit flared magwell designed for the Nerf Rapidstrike that's designed to blend in with the shape of the blaster around it. Examples of the mounting point methods can be seen from both Jase3D and BlasterTech, as is the form factor inspired by the former.
A flared magwell provides a larger margin of error to help guide magazines into the blaster, helping reduce fumbled reloads.
The author marked this model as their own original creation.