The single most useful thing to know about owning a G4 is that there is no such thing as a G4 coil. The coil is sealed inside the cartridge, and the cartridge is what you replace.
Searching for one returns results, because plenty of other people search for it too. That does not make the part exist. What you want is a GPP cartridge, and this page covers which one.
GPP, and what it fits
UWELL states that the GPP cartridge serves the G3, G4, and G5 families. One part covers three generations, which is unusually convenient and is the reason the platform is worth understanding rather than guessing at.
Four resistances are made: 0.4, 0.6, 0.9 and 1.2 ohms. The cartridge is on Replacement Pods. Nothing on Replacement Coils fits this device, because the coil is not a separate part on this platform.
The older Caliburn G and G2 work the other way round: an empty pod plus a coil you press in. If you have moved up from one of those, the buying habit changes with the device.
Which resistance, and the liquid that goes with it
The 0.9 and 1.2 ohm cartridges give a tighter mouth-to-lung draw at modest power. Twenty milligrams of nicotine salt at 50/50 is the match: ELFBAR ELFLIQ 10ml or BAR Salts.
The 0.4 and 0.6 open the draw out and pull considerably more liquid per puff. Ten milligrams is the sensible strength there, because the volume does the work the concentration was doing before. Running a 20mg bottle at 0.4Ω is how a pleasant liquid becomes a harsh one.
Two adjustments change the draw further: a slider on the body, and the cartridge itself, which can be loaded either way round. That second one is easy to miss and makes a real difference.
Power and screen
Up to thirty-five watts, adjustable; triple-click to enter the setting and change it on screen. The screen is a 0.85-inch colour panel with a puff counter and a day and night mode.
A 1300mAh cell charges over USB Type-C at 5V and 2A. It is sealed, so batteries are not a page this device needs; that shelf serves the mods here that take removable cells.
Cartridge life
A cartridge is a consumable, and what determines its life is overwhelmingly the liquid rather than the hardware. Sweet, dessert, and candy profiles coat a coil faster than plain fruits and menthols, and on a sealed cartridge that means replacing the whole part rather than a coil inside it.
The practical habit is to order cartridges alongside the liquid. On a device where the coil cannot be replaced separately, running out of cartridges stops the device outright.
Product and variant overview
One device, one cartridge platform, four resistances. The Caliburn G4 takes the GPP cartridge — shared with the G3 and G5 families — at 0.4, 0.6, 0.9 or 1.2 ohms.
Compatibility and related products
GPP also fits the G3 and G5 families, so a spare travels between them.
Liquid: 20mg salt at 50/50 on the 0.9 and 1.2 ohm cartridges; 10mg on the 0.6 and 0.4.
Buying guidance
Buy a cartridge, not a coil. The coil is inside the cartridge and is not sold on its own.
Match the strength to the resistance rather than to the device. Twenty milligrams at 0.4Ω is too much for most people.
A GPP cartridge bought for a G4 will also serve a G3 or a G5, which makes spares easy to justify.
Try the cartridge loaded the other way round before deciding the draw is wrong. It is a genuine adjustment.
Order cartridges with sweet liquids rather than after them.
Kenya and Nairobi relevance
One cartridge covering three device generations is a real advantage anywhere in Kenya where a part needs ordering rather than picking up, because a spare is never wasted. Nairobi dIspatch is same-day, with 24 to 48 hours elsewhere in Kenya.