Nerf Regulator. Select Fire, New Stock, 3 New Barrels. Two of them have Tac Rails. Most likely using the conveyer belt pusher system. : r/Nerf
What's the best modulus stock for ECS-10 : r/Nerf
Hasbro Nerf Modulus Regulator
Amazon.com: Nerf Modulus Regulator with Nerf N-Strike Elite Strongarm Blaster Bundle : Toys & Games
Amazon.com: NERF Modulus Recon MKIII Blaster, Removable Stock and Barrel Extension, Dart Shield, 12-Dart Clip, 12 Elite Darts, Outdoor Games and Toys for Boys and Girls (Amazon Exclusive) : Toys & Games