4 (フォー, Fō) is a Forge Disc released by Takara Tomy and Hasbro as part of the Burst System as well as the God Layer System and SwitchStrike System. It debuted in Japan with the release of the B-75 Booster Blaze Ragnaruk 4Cross Flugel on March 18th, 2017. It later debuted in western countries with the release of the SwitchStrike Starter Pack Wyvron W3 4Glaive Atomic.
4, like other even numbered Core Discs, is symmetrical and elliptical in shape in order to facilitate a Disc Frame. Each side features two protrusions, one molded into the shape of a "4" and the other molded into the shape of the Roman Numeral "IV". The protrusions extend further from the center more than other Core Discs which grants 4 high Outward Weight Distribution (OWD) and subsequent Stamina potential. As a Core Disc, 4 is comparatively heavier than regular Forge Discs such as Heavy and Gravity which grants higher Knock-Out Resistance and the ability to facilitate Disc Frames can add characteristics such as Life-After-Death with Cross or Glaive. While 7 has greater Stamina, 4's Stamina is still comparable.
Overall, 4 features high Stamina without the massive Burst risk posed by 8 and high weight for Knock-Out Resistance making the Core Disc a key part in Stamina, Defense and Attack Combinations. When paired with Frames such as Cross or Glaive, Combinations using 4 have high Life-After-Death as well.
As such, 4 is a must have for competitive bladers.
- B-75 Blaze Ragnaruk 4Cross Flugel
- B-80 Random Booster Vol. 6 Tornado Wyvern.4G.At - 01: Tornado Wyvern 4Glaive Atomic
- B-80 Random Booster Vol. 6 Tornado Wyvern.4G.At - 08: Beast Behemoth 4Cross Weight
- B-87 Random Booster Vol. 7 Maximum Garuda.8F.Fl - 05: Draciel Shield 4Flow Cycle
- B-87 Random Booster Vol. 7 Maximum Garuda.8F.Fl - 06: Dranzer Spiral 6Cross Spiral
- B-90 3on3 Battle Booster Set - Galaxy Zeus 4Meteor Planet
- B-95 Random Booster Vol. 8 Shelter Regulus.5S.Tw - 06: Quad Quetzalcoatl 4Star Flugel
- B-95 Random Booster Vol. 8 Shelter Regulus.5S.Tw - 08: Driger Slash 4Vortex Hunter
- B-98 God Customize Set - Deep Chaos 4Flow Bearing
- B-111 Random Booster Vol. 10 Crash Ragnaruk.11R.Wd - 03: Z Achilles 4 Destroy
- B-118 Random Booster Vol. 11 Vise Leopard.12L.Ds - 02: Vise Leopard 4 Yard
- B-130 Random Booster Vol. 13 Air Knight.12E.Et - 05: Hazard Kerbeus 4 Merge'
- B-132 Random Booster Vol. 14 Driger Fang.0.Xt - 07: Right Artemis 4Proof Orbit
- B-170 Random Booster Vol. 21 - 01: Death Diabolos 4Turn Merge' 1D
- B-178 Random Booster Vol. 24 - 08: Revive Phoenix 4 Metal Defense
- B-00 Premiere Set - Blaze Ragnaruk 4Cross Flugel (Premiere Set Ver.) (painted dark blue)
- B-00 Blaze Ragnaruk 4Cross Flugel (Premium Red Ver.) (wbba. Exclusive)
- B-00 Blaze Ragnaruk 4Star Blow (wbba. Store Exclusive)
- B-00 Emperor Forneus 4Glaive Hunter' (wbba. Store Exclusive)
- B-00 Legend Star Bey Set - Cho-Z Achilles 4Bump Yard
- E1028 Wyvron W3 4Glaive Atomic
- E1030 Roktavor R3 4Cross Flugel
- E1034 Genesis Valtryek V3 4Glaive Flugel
- E1042 Caynox C3 4Flow Bearing
- E2460 Shadow Snake Pit Battle Set - Legend Spryzen S3 4Cross Guard
- E4722 Lightning-X Istros I4 4 Accel-S
- E4734 Typhon T4 4 Defense-S
- E4746 Gold-X Betromoth B4 & Galaxy Zeutron Z4 Dual Pack - Galaxy Zeutron Z4 4 Liner-S
- E4752 Tornado-X Yegdrion Y4 & Morrigna M4 Dual Pack - Tornado-X Yegdrion Y4 4 Fusion-S
- E5957 Asteroid Zeutron Z3 4Meteor Revolve
- F0661 Slayer Showdown Battle Set - Triumph Devolos D6 4 Universe-SPM