The term “Doubler” is Definitely Confusing.
I guess it’s meaning is based on the context it’s used in.
For Tasty Vapor, they sell a 0mg Flavored PG|VG mix which they call it a “Doubler”. It has the same amount of Flavoring as their Nicotine e-Liquids just No Nicotine. It’s purpose is so a person can by a Flavored e-Liquid, say Tasty Finger 36mg, and then Dilute it to a Lower Nicotine Level, using the Tasty Finger “Doubler”, without any lose of Flavor.
But I have also seen e-Liquid Vendors who sell a “Doubler” which is a 100% Pure Flavoring Blend. So if you like the Vendor’s Pineapple Cheery Crème e-Liquid but would like it to be Stronger in Flavor, you can buy their Pineapple Cheery Crème “Doubler” and add a Few Drops to make the Flavor Stronger. The “Doubler” here is Entirely Flavorings in the Same Proportions as what the Vendors uses to make the Vendors Flavored e-Liquids.
All so Confusing isn’t it?
BTW – Tasty Vapor Doublers are Great to Have around. In that it is Easy to make DIY’s from them because the PG|VG is already flavored. You just add your own Unflavored Nicotine Base and Flavor/Sweeten to taste using your own Flavor Concentrates.
Or you can also use them when you want to vape 0mg like at night.
And at 15 bucks for 4oz (120ml) they are Very Inexpensive.
BTW2 - The Flavorings that I have seen at VaporBomb are Blends of 100% Flavoring Concentrates.