I've been comparing research peptide suppliers recently, and one thing I've noticed is that price alone isn't enough to evaluate a vendor. When I look at a supplier, I usually focus on documentation, testing information, batch details, and overall transparency before comparing the final price. One supplier I've been researching is PS Peptides, so I'm interested in how other members approach supplier evaluation. What I Check First My basic checklist is: Product information Certificate of Analysis (COA) Batch or lot information Laboratory information Analytical testing Shipping information Customer support Final price COAs and Testing For me, the COA is one of the most important things to review. I'd want to see information such as: Product identification Batch number Testing laboratory Testing date Analytical method Reported results I also pay attention to references to testing methods such as HPLC and mass spectrometry. Rather than simply accepting a statement that something is "lab tested," I'd prefer to review the actual report and understand what was tested. Batch Information I think batch traceability is particularly useful. Ideally, the information should connect: Product → Batch → Laboratory → Testing Method → Result That gives considerably more context than a generic purity claim. Price and Promotions After evaluating the supplier information, I compare the final price. PS Peptides currently has a promotional code: LOOT30 If someone is already considering PS Peptides, they can check whether the code is currently applicable during checkout. I wouldn't choose a supplier solely because of a discount, though. I'd treat the promotion as a pricing factor after evaluating the supplier itself. What Do You Look For? For people here who have experience comparing research peptide vendors, what matters most to you? Batch-specific COAs? Independent laboratory testing? HPLC? Mass spectrometry? Endotoxin testing? Laboratory identity? Batch consistency? Shipping and storage information? Price? And do you consider a supplier-provided COA sufficient for initial supplier screening, or do you think independent verification should be considered whenever practical?