Order 500 empty pods, fill them with your HHC distillate, and watch half of them clog within two days. That’s not a bad batch — it’s the wrong coil for the oil you’re filling.

We ship thousands of empty pods a month to CBD and HHC brands across Europe, and the coil question comes up on almost every call. The short answer: if you’re filling anything thicker than standard e-liquid, go ceramic. The reasons why, and the one case where cotton still makes sense, are below.

How Ceramic Coils Work

A ceramic coil is a block of sintered ceramic wrapped around a heating wire — think of it as a fine stone sponge. Oil moves into the pores through capillary action, the wire heats the ceramic, and the oil vaporizes from inside the porous structure rather than off the surface.

That structure matters for thick oil in three ways. Ceramic spreads heat evenly across a wide surface, so there are no hot spots to burn the oil and cause a harsh taste. The pores wick oil slowly and steadily, so the coil doesn’t flood when warm or starve when cold — the patience thick distillate needs. And ceramic doesn’t degrade the way organic material does: a well-made ceramic pod handles 300+ puffs before performance drops off.

3.2ml max capacity ceramic empty pod cartridge with flat mouthpiece, compatible with RELX and ZGAR (Bingxiong) devices — Ceramic-coil empty pod, 3.2ml. The porous ceramic structure lets thick oil wick steadily instead of flooding or drying out the coil.

Where Cotton Falls Short

Cotton coils wrap organic cotton fibre around a heating wire. For standard e-liquid — 50/50 VG/PG, nicotine salt — that works fine: it wicks fast, the pods are cheap, and flavor holds up.

Thick oil is a different story. High-viscosity distillate doesn’t flow into cotton fibre the way thin e-liquid does, so the cotton saturates unevenly and creates dry spots that burn. Once a spot burns, the pod is dead. The inconsistent draw leading up to that point — a strong pull, then nothing, then a mouthful of vapor — is what kills repeat purchases fastest. Cotton also degrades faster under thick oil: expect 100–150 puffs before noticeable decline, roughly half of what ceramic delivers.

Real Numbers: Ceramic vs Cotton

	Ceramic Coil	Cotton Coil
Best oil viscosity	Thick (60%+ distillate)	Thin to medium (e-liquid, thin CBD)
Avg. puff life	300–500 puffs	100–200 puffs
Flavor consistency	Stable through life	Drops after ~100 puffs
Clogging risk	Low (with proper inlet design)	High with thick oils
Burn risk	Very low	Moderate to high
Cost per unit	$0.05–0.15 more than cotton	Cheapest option
Best use case	HHC, CBD distillate, live resin, concentrates	Nicotine salt, thin CBD tincture

When Cotton Still Makes Sense

Cotton isn’t obsolete — it’s just built for a narrower job. Choose it when you’re filling thin oil (standard e-liquid or a heavily diluted CBD tincture), when per-unit cost matters more than longevity, or when you’re building a disposable-style product where 100 puffs is the expected life anyway.

Choose ceramic when your oil is thick, your customers expect 300+ puffs, or you’re building a brand people come back to rather than a one-time sale. Across the CBD and HHC brands we work with in Europe, roughly 95% land on ceramic, and most of the ones who start on cotton switch after their first batch.

Inlet Holes Matter as Much as Coil Type

Coil type is only half the equation. The inlet holes — the small openings that let oil flow from the reservoir to the coil — decide whether thick distillate reaches the ceramic at all. Standard round holes work for thin oil, but thick distillate needs flower-pattern inlets: several small holes arranged in a rosette that spread the load so no single hole clogs with a thick globule. Our duck-bill concentrate cartridges (0.5ml, 0.6ml, 1.2ml) use flower-pattern inlets for this reason, while the standard 2ml pods use optimized round inlets that handle most medium-to-thick oils without issue.

Bulk 0.8ml empty pod cartridge with flower leak-proof inlet compatible with RELX Infinity for golden ratio HHC distillate distribution. — R12 — 0.8ml ceramic coil concentrate pod with flower-pattern inlet, built for HHC distillate and thick CBD oil.

What to Order Based on Your Fill

Fill Type	Recommended Hardware
CBD oil (medium viscosity)	RELX-compatible R04–R06, 2.0ml, ceramic, standard inlets
HHC distillate or full-spectrum CBD (thick)	510 cartridge SKU 2101, 1.0ml, 4×2.0mm inlet, 1.2Ω ceramic
Pure distillate / live resin (very thick)	Duck-bill concentrate cartridges R11–R13, flower-pattern inlets
Thin CBD tincture or nicotine salt	RELX-compatible R01–R03, 1.8ml, mesh coil

Not sure which fits? That’s what the sample pack is for — $120 flat, DHL to EU/UK included, up to five styles at 20 pcs each. Fill them with your own oil, run them for a week, and order the winner in bulk.