When you're buying vapes in bulk, nicotine strength isn't just a spec—it's a promise to your customers. You need to verify what the label says is actually true. Always ask for a certificate of analysis (COA) for each batch, check the batch code on the packaging, and understand whether it's salt or freebase nicotine. If a supplier can't provide a COA, that's a red flag. And don't forget storage: heat and light degrade nicotine, so keep your stock cool and dark.