As others indicated, try to look for a seller who has a copy of a COA listing purity for the batch they are selling. Good vendors will have one posted from a trusted testing facility like Janoshik. Look for a fairly recent test. Some lesser selling items may have older but still valid COAs, while the most popular will have very recent certificates. If you are really worried don't shop China direct sources, choose a US vendor. US vendors for the most part are re-selling cheap Chinese peptides at a jacked up price, but at least you don't have to worry about tariffs, customs and international shipping. You will mostly have labels on your vials (except for some like Nexaph 10 vial kits, which come without) which eliminates concern over what you are getting. Everyone has to decide what level of risk they are willing to take when it comes to buying grey market.