Oil cartridges are used in conjunction with oil vape pens. Oil cartridges can be prefilled or refillable and can come in a variety of flavors and strengths all adjustable to the vapers tastes. Oil cartridges will require a vape with higher wattage than for dry herb or even wax but this is usually not a problem. Vape pens compatible for oil cartridges are able to reach those temperatures/power levels. Most importantly, be careful when filling or refilling the cartridge because oil can be sticky and gross when it spills.