Hyper Ammo Nearly Confirmed to be about 13-14mm, pics found by Piggy - SG : r/Nerf
MASSTIMO Toy Gun for Nerf Gun Target with 100 Round Refill Compatible with Nerf Hyper Rounds Darts, Kid Indoor Outdoor Shooting Game Toy : Amazon.co.uk: Toys & Games
Worker Ammo Rival Rounds – Out of Darts
Review: Fake Nerf Rival Balls/Rounds (Cheaper but are they as good?) - YouTube
100Pcs Nerf Darts Refill Nerf Bullets Round Head Blasters For Nerf Gun – Quildinc
NEW 20 Foam Ammo Disc Refill Darts Discs for Shooting Toy Christmas Stocking | eBay