Cheap old school neoprene belts. Both Dayco & Gates offer value line belts i.e Duralast, Drive Rite, Napa Power Fit etc. OEM's and the top line name brands use EPDM belts in the premium products for long life. I always figure something that can leave me dead on the road needs a OEM/premium grade part. Swap them for a top grade Dayco or Gates within a year or two. FYI-I sold parts for 32+ years and I never recommend value line parts unless you are dumping the vehicle within a year.
Dave