The same compound in 5 mg and 10 mg vials is two SKUs. Batches sit underneath SKUs: one SKU can have several batches in stock at once.
SKU
A code for one sellable product variant, such as a compound in one vial size.
See it running on your own catalog
Purity does the work these terms describe: batches held until their lab report is in, payments matched to orders, and wording checked before it sends.