Strength differs not just between brands yet also for flavors of the very same brand. Companies like Flavourart and Inawera are infamous for their powerful concentrates, where 1-2% is sufficient to dominate a dish-- but even some of their own can be used in the 5-10% variety. A great indicator of potency is the "ordinary mixing quantity" portion, which can be found on each flavor's web page at ELR.
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