Gold-X Betromoth B4 is an Energy Layer released as part of the Burst System as well as the SlingShock System. It debuted in western countries with the release of the Gold-X Betromoth B4 & Galaxy Zeutron Z4 Dual Pack.
Gold-X Betromoth B4, as its name implies, is a SlingShock-Exclusive variant of Betromoth B2 that's reclassified as a Stamina Type Energy Layer. However, despite the "Gold-X" prefix and "B4" suffix, its design is unchanged from its Dual Layer counterpart, and the only difference between them are their color schemes. Unlike the color scheme of Betromoth B2, Gold-X Betromoth B4's colors scheme consists of a clear, five-bladed top-layer with gold and silver paint apps on top of each blade, a gold bottom-layer with double-sided jaw-like arches, and a gold beast-like head with silver eyes that's depicted biting down on the "B" in the center of the Layer as it faces forward. Akin to Lightning-X Istros I4, and unlike all other SlingShock-Exclusive Dual Layers, Gold-X Betromoth B4 does not feature glitter of any kind that's infused into the Layer's clear plastic. Aside from this, like all other SlingShock-Exclusive Dual Layers, the "B" in the center of Gold-X Betromoth B4 is transparent while the rest is colored green. Aside from the absence of glitter, these details enforce the "Gold-X" motif of the Layer's prefix, but not for its "B4" suffix. Like Betromoth B2, the gold beast-like head of Gold-X Betromoth B4 represents its original Takara Tomy namesake; the Behemoth, a primal unconquerable monster that's featured in the Bible.
For more in-depth information on performance, one should refer to the Betromoth B2 page.