We first started using Acro Biosystem's recombinant proteins to develop strain-specific SARS-CoV-2 ELISAs during the 2019 pandemic and have found their products to be of high quality, giving us reliable and consistent data. Product information is clear and easily accessible, and delivery and customer service have been excellent. We will continue to use Acro Biosystems as a source of recombinant proteins when developing assays.