The vast majority of CBD oils come in bottles measuring either 15 milliliters (mL), or 0.5 ounces; or 30 mL, or 1 ounce. However, CBD concentration is more important than bottle size. Concentration refers to the ratio of hemp oil solution (measured in mL) compared to the amount of CBD cannabinoid (measured in milligrams, or mg). A 15-mL bottle may contain 100 mg of CBD, 300 mg, 500 mg, or more. The higher the mg amount, the stronger the CBD oil will be. For this reason, the ‘mg’ measurement is also referred to as the oil’s strength; i.e., 400-mg oil might be called 400-strength oil.
Never pick a brand based on one person's opinion on social media. Especially if you feel like you are getting a sales pitch. There are many scammers and multi-level marketing salespeople that use Facebook and other social media outlets to push a particular product. Many of them will tell you whatever you want to hear to get you to buy from them. Be wary of their claims and testimonials.
As mentioned above, CBD is no longer considered a Schedule I controlled substance under the Farm Act. However, under the DEA’s definition, it remains on the list. This allows for individual states to create exceptions to the status of CBD, even when cultivated from hemp plants grown legally under the act. It also maintains illegal status for any CBD sourced from plants produced in settings that are not consistent with that Act, or by an unlicensed grower. It is expected that more clarification on the status of CBD will come early this year (2019).