The smallest one on the Can Fan filter Family picture is perfect enough for small indoor gardens (max. 2 square meter).
Carbon Filters are activated carbon filters designed to remove volatile organic compounds from the air. A variety of sizes are available to fit everyone's personal needs.
The activated carbon within the CAN Filter removes 99.5% of all volatiles from the air.
The filter size required for you application will depend on the amount of air flow required for your application. Two rules of thumb are to maintain an air flow that is eight to ten times the total volume of your vented space per hour, or, for indoor growing applications, 150 CFM per 1000 watt light bulb
Get one fast it's really worth the money.