Nerf Rival Vision XXII-800 Blaster, Most Accurate Nerf Rival System, Adjustable Sight, 8 Nerf Rival Accu-Rounds - Nerf
left the one on the left in the melting snow, and apparently rival balls are similar to sponges. they are off brand so maybe that has something to do with it. :
Nerf Hyper Rush-40, Siege-50 and Mach-100 review: where the rubber meets the foam - The Verge
NERF HYPER BLASTERS REVEALED : r/Nerf
Amazon.com: NERF Hyper Mach-100 Fully Motorized Blaster, 80 Hyper Rounds, Eyewear, Up to 110 FPS Velocity, Easy Reload, Holds Up to 100 Rounds
Nerf Hyper Rush-40, Siege-50 and Mach-100 review: where the rubber meets the foam - The Verge
Amazon.com: NERF Hyper 200-Round Refill Includes 200 Hyper Rounds, for Use Hyper Blasters, Stock Up Hyper Games : Toys & Games
Nerf Hyper Rush-40, Siege-50 and Mach-100 review: where the rubber meets the foam - The Verge