These jars are perfect for storing cannabis in. The jars are completely opaque so no light gets inside the jars. The jars DO have an airtight seal. I stored a humidity pack in each jar where the humidity pack lasted well over a year without drying out. These jars are also smell proof. Although the lids are plastic, they do have a airtight seal. I found that these jars hold alittle bit more than an ounce. I would say maybe an ounce and a fourth of cannabis. I've had cannabis stay fresh well over 7 months in this jar. Longest lasting being 15ish months before cannabis starts to lose its freshness and flavor. Will buy again if anything happens to the jars.